89C51单片机英文说明论文英文翻译部分

英文翻译系别专业班级学生姓名学号指导教师Introduction and application of AT89C51 Microcontrollers are used in a multitude of commercial applications such as modems, motor-control systems, air conditioner control systems, automotive engine and among others. The high processing speed and enhanced peripheral set of these microcontrollers make them suitable for such high-speed event-based applications. However, these critical application domains also require that these microcontrollers are highly reliable. The high reliability and low market risks can be ensured by a robust testing process and a proper tools environment for the validation of these microcontrollers both at the component and at the system level. Intel Plaform Engineering department developed an object-oriented multi-threaded test environment for the validation of its AT89C51 automotive microcontrollers. The goals of this environment was not only to provide a robust testing environment for the AT89C51 automotive microcontrollers, but to develop an environment which can be easily extended and reused for the validation of several other future microcontrollers. The environment was developed in conjunction with Microsoft Foundation Classes (AT89C51).The paper describes the design and mechanism of this test environment, its interactions with various hardware/software environmental components, and how to use AT89C51.1. IntroductionThe 8-bit AT89C51 CHMOS microcontrollers are designed to handle high-speed calculations and fast input/output operations. MCS 51 microcontrollers are typically used for high-speed event control systems. Commercial applications include modems, motor-control systems, printers, photocopiers, air conditioner control systems, disk drives, and medical instruments. The automotive industry use MCS 51 microcontrollers in engine-control systems, airbags, suspension systems, and antilock braking systems (ABS).The AT89C51 is especially well suited to applications that benefit from its processing speed and enhanced on-chip peripheral functions set, such as automotive power-train control, vehicle dynamic suspension, antilock braking, and stability control applications. Because of these critical applications, the market requires a reliable cost-effective controller with a low interrupt latency response, ability to service the high number of time and event driven integrated peripherals needed in real time applications, and a CPU with above average processing power in a single package. The financial and legal risk of having devices that operate unpredictably is very high. Once in the market, particularly in mission critical applications such as anautopilot or anti-lock braking system, mistakes are financially prohibitive. Redesign costs can run as high as a $500K, much more if the fix means back annotating it across a product family that share the same core and/or peripheral design flaw. In addition, field replacements of components is extremely expensive, as the devices are typically sealed in modules with a total value several times that of the component. To mitigate these problems, it is essential that comprehensive testing of the controllers be carried out at both the component level and system level under worst case environmental and voltage conditions.This complete and thorough validation necessitatesnot only a well-defined process but also a proper environment and tools to facilitate and execute the mission successfully.Intel Chandler Platform Engineering group provides postsilicon system validation (SV) of various micro-controllers and processors. The system validation process can be broken into three major parts.The type of the device and its application requirements determine which types of testing are performed on the device.The AT89C51 provides the following standard features: 4Kbytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bittimer/counters, a five vector two-level interrupt architecture,a full duple ser -ial port, on-chip oscillator and clock circuitry.In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters,serial port and interrupt sys -tem to continue functioning. The Power-down Mode saves the RAM contents but freezes the oscil -lator disabling all other chip functions until the next hardware reset.Pin Configurations Block Diagram2 Pin DescriptionVCC Supply voltage.GND Ground.Port 0Port 0 is an 8-bit open-drain bi-directional I/O port. As an output port, each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high impedance inputs.Port 0 may also be configured to be the multiplexed low order address/data bus during accesses to external program and data memory. In this mode P0 has internal pullups.Port 0 also receives the code bytes during Flash programming, and outputs the code bytes during program verification. External pullups are required during program verification.Port 1Port 1 is an 8-bit bi-directional I/O port with internal pullups.The Port 1 output buffers can sink/so -urce four TTL inputs.When 1s are written to Port 1 pins they are pulled high by the internal pullups and can be used as inputs. As inputs, Port1 pins that are externally being pulled low will source current (IIL) because ofthe internal pullups.Port 1 also receives the low-order address bytes during Flash programming and verification.Port 2Port 2 is an 8-bit bi-directional I/O port with internal pullups.The Port 2 output buffers can sink/source four TTL inputs.When 1s are written to Port 2 pins they are pulled high by the internal pullups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pullups.Port 2 emits the high-order address byte during fetches from external program memory and during accesses to Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pullups.Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses (MOVX @DPTR). In this application, it uses strong internal pull-ups when emitting 1s.During accesses to external data memory that use 8-bit addresses (MOVX @ RI), Port 2 emitsthe contents of the P2 Special Function Register.Port 2 also receives the high-order address bits and some control signals durin Flash programming and verification.Port 3Port 3 is an 8-bit bi-directional I/O port with internal pullups.The Port 3 output buffers can sink/sou -rce four TTL inputs.When 1s are written to Port 3 pins they are pulled high by the internal pullups and can be used as inputs. As inputs,Port 3 pins that are externally being pulled low will source current (IIL) because of the pullups. Port 3 also serves the functions of various special featuresof the AT89C51 as listed below:3 Port Pin Alternate FunctionsP3.0 RXD(serial input port)P3.1 TXD (serial output port)P3.2 INT0 (external interrupt 0)P3.3 INT1 (external interrupt 1)P3.4 T0 (timer 0 external input)P3.5 T1 (timer 1 external input)P3.6 WR (external data memory write strobe)P3.7 RD (external data memory read strobe)Port 3 also receives some control signals for Flash programming and verification. RSTReset input. A high on this pin for two machine cycles while the oscillator is running resets the device.ALE/PROGAddress Latch Enable output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG)during Flash programming.In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency, and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped duri -ng each access to external DataMemory.If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode.PSENProgram Store Enable is the read strobe to external program memory. When the AT89C51 is executing code from external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory.EA/VPPExternal Access Enable. EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset.EA should be strapped to VCC for internal program executions. This pin also receives the 12-volt programming enable voltage (VPP) during Flash programming, for parts that require 12-volt VPP.XTAL1Input to the inverting oscillator amplifier and input to the internal clock operating circuit.XTAL2Output from the inverting oscillator amplifier.4 Oscillator CharacteristicsXTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier which can be configured for use as an on-chip oscillator, as shown in Figure 1. Either a quartz crystal or ceramic resonator may be used. To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 is driven as shown in Figure 2.There are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high and low time specifications must be observed.Idle ModeIn idle mode, the CPU puts itself to sleep while all the onchip peripherals remain active. The mode is invoked by software. The content of the on-chip RAM and all the special functions registers remain unchanged during this mode. The idle mode can be terminated by any enabled interrupt or by a hardware reset. It should be noted that when idle is terminated by a hard ware reset, the device normally resumes program execution, from where it left off, up to two machine cycles before the internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this event, but access to the port pins is not inhibited. To eliminate the possibility of an unexpected write to a port pin when Idle is terminated by reset, theinstruction following the one that invokes Idle should not be one that writes to a port pin or to external memory.Figure 1. Oscillator Connections Figure 2. External Clock Drive Configuration Note: C1, C2 = 30 pF . .10 pF for Crystals = 40 pF . .10 pF for Ceramic Resonators In the power-down mode, the oscillator is stopped, and the instruction that invokes.5 Power-down Modepower-down is the last instruction executed. The on-chip RAM and Special Function Registers retain their values until the power-down mode is terminated. The only exit from power-down is a hardware reset. Reset redefines the SFRs but does not change the on-chip RAM. The reset should not be activated before VCC is restored to its normal operating level and must be held active long enough to allow the oscillator to restart and stabilize.Status of External Pins During Idle and Power-down Modes Mode Program Memory ALE PSEN PORT0 PORT1 PORT2 PORT3Idle Internal 1 1 Data Data Data DataIdle External 1 1 Float Data Address DataPower-down Internal 0 0 Data Data Data DataPower-down External 0 0 Float Data Data DataProgram Memory Lock BitsOn the chip are three lock bits which can be left unprogrammed (U) or can be programmed (P) to obtain the additional features listed in the table below.Lock Bit Protection Modes Program Lock Bits Protection Type LB1 LB2 LB31 U U U No program lock features2 P U U MOVC instructions executed from external program memory are disabled from etching code bytes from internal memory.3 P P U Same as mode 2, also verify is disabled4 P P P Same as mode 3, also external execution is disabledWhen lock bit 1 is programmed, the logic level at the EA pin is sampled and latched during reset. If the device is powered up without a reset, the latch initializes to a random value, and holds that value until reset is activated. It is necessary that the latched value of EA be in agreement with the current logic level at that pin in order for the device to function properly.6 Programming the FlashThe AT89C51 is normally shipped with the on-chip Flash memory array in the erased state (that is, contents = FFH) and ready to be programmed. The programming interface accepts either a high-voltage (12-volt) or a low-voltage (VCC) program enable signal. The low-voltage programming mode provides a convenient way to program the AT89C51 inside the user’s system, while the high-voltage programming mode is compatible with conventional thirdparty Flash or EPROM programmers. The AT89C51 is shipped with either the high-voltage or low-voltage programming mode enabled. The respective top-side marking and device signature codes are listed in the following table.VPP = 12V VPP = 5VTop-Side Mark AT89C51 AT89C51xxxx xxxx-5yyww yywwSignature (030H) = 1EH (030H) = 1EH(031H) = 51H (031H) = 51H(032H) =F FH (032H) = 05HThe AT89C51 code memory array is programmed byte-bybyte in either programming mode. To program any nonblank byte in the on-chip Flash Memory, the entire memory must be erased using the Chip Erase Mode.7 Programming AlgorithmBefore programming the AT89C51, the address, data and control signals should be set up according to the Flash programming mode table and Figure 3 and Figure 4. To program the AT89C51, take the following steps.1. Input the desired memory location on the address lines.2. Input the appropriate data byte on the data lines.3. Activate the correct combination of control signals.4. Raise EA/VPP to 12V for the high-voltage programming mode.5. Pulse ALE/PROG once to program a byte in the Flash array or the lock bits. The byte-write cycle is self-timed and typically takes no more than 1.5 ms. Repeat steps 1 through 5, changing the address and data for the entire array or until the end of the object file is reached.Data Polling:The AT89C51 features Data Polling to indicate the end of a write cycle. During a write cycle, an attempted read of the last byte written will result in the complement of the written datum on PO.7. Once the write cycle has been completed, true data are valid on all outputs, and the next cycle may begin. Data Polling may begin any time after a write cycle has been initiated.Ready/Busy:The progress of byte programming can also be monitored by the RDY/BSY output signal. P3.4 is pulled low after ALE goes high during programming to indicate BUSY. P3.4 is pulled high again when programming is done to indicateREADY.Program Verify: If lock bits LB1 and LB2 have not been programmed, the programmed code data can be read back via the address and data lines for verification.The lock bits cannot be verified directly. Verification of the lock bits is achieved by observing that their features are enabled.8 Flash Programming ModesMode RST PSEN ALE/PROG EA/VPP P2.6 P2.7 P3.6 P3.7Write Code Data H L H/12V L H H HRead Code Data H L H H L L H HWriteLockBit -1 H L H/12V H H H HBit -2 H L H/12V H H L LBit -3 H L H/12V H L L LChip Erase H LH/12V H L L LRead Signature Byte H L H H L L L LNote: 1. Chip Erase requires a 10 ms PROG pulse.Figure 3. Programming the Flash Figure 4. Verifying the FlashFlash Programming and Verification Waveforms -High-voltage Mode (VPP = 12V) Flash Programming and Verification Waveforms -Low-voltage Mode (VPP = 5V)9 Chip EraseThe entire Flash array is erased electrically by using the proper combination of control signals and by holding ALE/PROG low for 10 ms. The code array is written with all “1”s. The chip erase operation must be executed befor e the code memory can be re-programmed.Reading the Signature Bytes:The signature bytes are read by the same procedure as a normal verification of locations 030H, 031H, and 032H, except that P3.6 and P3.7 must be pulled to a logic low. The values returned areas follows.(030H) = 1EH indicates manufactured by Atmel(031H) = 51H indicates 89C51(032H) = FFH indicates 12V programming(032H) = 05H indicates 5V programmingProgramming InterfaceEvery code byte in the Flash array can be written and the entire array can be erased by using the appropriate combination of control signals. The write operation cycle is selftimed and once initiated, will automatically time itself to completion. Flash Programming and Verification Characteristics TA = 0°C to 70°C, VCC = 5.0 . .10%10 Symbol Parameter Min Max UnitsVPP(1) Programming EnableV oltage11.5 12.5 VIPP(1) Programming Enable Current 1.0 mA1/tCLCL Oscillator Frequency 3 24 MHztA VGL Address Setup to PROGLow48tCLCLtGHAX Address Hold After PROG 48tCLCLtDVGL Data Setup to PROG Low 48tCLCLtGHDX Data Hold After PROG 48tCLCLtEHSH P2.7(ENABLE) High to VPP 48tCLCLtSHGL VPP Setup to PROG Low 10 μstGHSL(1) VPP Hold After PROG 10 μstGLGH PROG Width 1 110 μstA VQV Address to Data Valid 48tCLCLtELQV ENABLE Low to Data Valid 48tCLCLtEHQZ Data Float After ENABLE 0 48tCLCLtGHBL PROG High to BUSY Low 1.0 μstWC Byte Write Cycle Time 2.0 msNote: 1. Only used in 12-volt programming mode.Absolute Maximum Ratings*Operating Temperature......................... -55°C to +125°CStorage Temperature ............................. -65°C to +150°CV oltage on Any Pin with Respect to Ground ............-1.0V to +7.0VMaximum Operating V oltage .................................. 6.6VDC Output Current....................................... 15.0 mA11 DC CharacteristicsTA = -40°C to 85°C, VCC = 5.0V . .20% (unless otherwise noted)Symbol Parameter Condition Min Max Units VIL Input Low-voltage (Except EA) -0.5 0.2 VCC 0.1 -VVIL1 nput Low-voltage (EA) -0.5 0.2 VCC 0.3 -VVIH iput High-voltage (Except XTAL1, RST) 0.2 VCC +0.9 VCC + 0.5 VVIH1 Input High-voltage (XTAL1, RST) 0.7 VCC VCC + 0.5 VVOL Output Low-voltage(1) (Ports 1,2,3) IOL = 1.6 mA 0.45 VVOL1 Output Low-voltage(1) (Port 0, ALE, PSEN) IOL = 3.2 mA 0.45 VVOH Output High-voltage (Ports 1,2,3, ALE, PSEN) IOH = -60 μA, VCC = 5V . .10% 2.4 VIOH = -25 μA 0.75 VCC VIOH = -10 μA 0.9 VCC VVOH1 Output High-voltage (Port 0 in External Bus Mode) IOH = -800 μA, VCC = 5V . .10% 2.4 VIOH = -300μA, 0.75 VCC VIOH = -80μA, 0.9 VCC VIIL Logical 0 Input Current (Ports 1,2,3)VIN = 0.45V -50 μ AITL Logical 1 to 0 Transition Current (Ports 1,2,3) VIN = 2V, VCC = 5V . .10% -650 μ AILI Input Leakage Current (Port 0, EA) 0.45 < VIN < VCC . 10 μ A RRST Reset Pull-down Resistor 50 300 K.CIO Pin Capacitance Test Freq. = 1 MHz, TA = 25°C 10 pFICC Power Supply Current Active Mode, 12 MHz 20 mA Idle Mode, 12 MHz 5 mA Power-down Mode(2) VCC = 6V 100 μ A VCC = 3V 40 μ A12 AC CharacteristicsUnder operating conditions, load capacitance for Port 0, ALE/PROG, and PSEN = 100 pF; load capacitance for all other outputs = 80 pF.External Program and Data Memory Characteristics Symbol ParameterFrequency 12 MHz Oscillator 16 to 24 MHz Oscillator Units Min Max Min Max 1/tCLCL Oscillator 0 24 MHztLHLL ALE Pulse Width 127 2tCLCL-40 40 ns nstA VLL Address Valid to ALE Low 43 tCLCL-13 nstLLAX Address Hold After ALE Low 48 tCLCL-20 nstLLIV ALE Low to Valid Instruction In 233 4tCLCL-65 nstLLPL ALE Low to PSEN Low 43 tCLCL-13 nstPLPH PSEN Pulse Width 205 3tCLCL-20 nstPLIV PSEN Low to Valid Instruction In 145 3tCLCL-45 nstPXIX Input Instruction Hold After PSEN 0 0 nstPXIZ Input Instruction Float After PSEN 59 tCLCL-10 nstPXA V PSEN to Address Valid 75 tCLCL-8 nstA VIV Address to Valid Instruction In 312 5tCLCL-55 nstPLAZ PSEN Low to Address Float 10 10 nstRLRH RD Pulse Width 400 6tCLCL-100 nstWLWH WR Pulse Width 400 6tCLCL-100 nstRLDV RD Low to Valid Data In 252 5tCLCL-90 nstRHDX Data Hold After RD 0 0 ns 13tRHDZ Data Float After RD 97 2tCLCL-28 nstLLDV ALE Low to Valid Data In 517 8tCLCL-150 nstA VDV Address to Valid Data In 585 9tCLCL-165 nstLLWL ALE Low to RD or WR Low 200 300 3tCLCL-50 3tCLCL+50 nstA VWL Address to RD or WR Low 203 4tCLCL-75 nstQVWX Data Valid to WR Transition 23 tCLCL-20 nstQVWH Data Valid to WR High 433 7tCLCL-120 nstWHQX Data Hold After WR 33 tCLCL-20 nstRLAZ RD Low to Address Float 0 0 nstWHLH RD or WR High to ALE High 43 123 tCLCL-20 nsExternal Program Memory Read CycleExternal Data Memory Read CycleExternal Data Memory Write Cycle External Data Memory Write CycleExternal Clock Drive WaveformsExternal Clock DriveSymbol Parameter Min Max Units1/tCLCL Oscillator Frequency 0 24 MHztCLCL Clock Period 41.6 nstCHCX High Time 15 nstCLCX Low Time 15 nstCLCH Rise Time 20 nstCHCL Fall Time ns 20 nsSerial Port Timing:Shift Register Mode Test Conditions(VCC = 5.0 V . .20%; Load Capacitance = 80 pF)Symbol Parameter 12 MHz Osc Variable Oscillator Units UnitsMin Max Min MaxtXLXL Serial Port Clock Cycle Time 1.0 12tCLCL μstQVXH Output Data Setup to Clock Rising Edge 700 10tCLCL-133 nstXHQX Output Data Hold After Clock Rising Edge 50 2tCLCL-117 nstXHDX Input Data Hold After Clock Rising Edge 0 0 nstXHDV Clock Rising Edge to Input Data Valid 700 10tCLCL-133 ns 13 ShiftRegister Mode Timing Waveforms AC Testing Input/Output Waveforms Float WaveformsA microcomputer interface converts information between two forms. Outside the microcomputer the information handled by an electronic system exists as a physical signal, but within the program, it is represented numerically. The function of any interface can be broken down into a number of operations which modify the data in some way, so that the process of conversion between the external and internal forms is carried out in a number of steps.An analog-to-digital converter(ADC) is used to convert a continuously variable signal to a corresponding digital form which can take any one of a fixed number of possible binary values. If the output of the transducer does not vary continuously, no ADC is necessary. In this case the signal conditioning section must convert the incoming signal to a form which can be connected directly to the next part of the interface, the input/output section of the microcomputer itself.Output interfaces take a similar form, the obvious difference being that here the flow of information is in the opposite direction; it is passed from the program to the outside world. In this case the program may call an output subroutine which supervises the operation of the interface and performs the scaling numbers which may be needed for a digital-to-analog converter(DAC). This subroutine passes information in turn to an output device which produces a corresponding electrical signal, which could be converted into analog form using a DAC. Finally the signal is conditioned(usually amplified) to a form suitable for operating an actuator.The signals used within microcomputer circuits are almost always too small to be connected directly to the “outside world” and some kind of interface must be used to translate them to a more appropriate form. The design of section of interface circuits is one of the most important tasks facing the engineer wishing to apply microcomputers. We have seen that in microcomputers information is represented as discrete patterns of bits; this digital form is most useful when the microcomputer is to be connected to equipment which can only be switched on or off, where each bit might represent the state of a switch or actuator.To solve real-world problems, a microcontroller must have more than just a CPU, a program, and a data memory. In addition, it must contain hardware allowing the CPU to access information from the outside world. Once the CPU gathers information and processes the data, it must also be able to effect change on some portion of the outside world.These hardware devices, called peripherals, are the CPU’s window to theoutside. The most basic form of peripheral available on microcontrollers is the general purpose I70 port. Each of the I/O pins can be used as either an input or an output. The function of each pin is determined by setting or clearing corresponding bits in a corresponding data direction register during the initialization stage of a program. Each output pin may be driven to either a logic one or a logic zero by using CPU instructions to pin may be viewed (or read.) by the CPU using program instructions.Some type of serial unit is included on microcontrollers to allow the CPU to communicate bit-serially with external devices. Using a bit serial format instead of bit-parallel format requires fewer I/O pins to perform the communication function, which makes it less expensive, but slower. Serial transmissions are performed either synchronously or asynchronously.AT89C51的介绍及运用单片机广泛应用于商业：诸如调制解调器，电动机控制系统，空调控制系统,汽车发动机和其他一些领域。

关于单片机at89c51的外文翻译5000字英文篇一：毕业设计外文翻译单片机AT89C51附件1：外文资料翻译译文AT89C51主要性能参数：与MCS-51产品如前所述完全兼容4K字节可重檫写Flash闪速存储器1000次檫写周期全静态操作：0HZ-24MHZ三级加密程序存储器128*8字节内部RAM32个可编程I/O口线2个16位定时/记数器6个中断源可编程串行UART通道低功耗空闲和掉电操作方式功能特性概述：AT89C51提供更多以下标准功能：4K字节Flash闪速存储器，128字节内部RAM，32个I/O口线，两个16位定时/记数器，一个5向量两级中断结构，一个全双工串行通信口，片内振荡器妥善钟电路。

同时，AT89C51可降至0HZ的静态逻辑操作，并支持两种软件可选的节电工作模式。

空闲方式停止CPU的工作，但允许RAM，定时/记数器，串行通信口及中断系统继续工作。

掉电方式保存RAM中的内容，但振荡器停止工作直到下一个硬件逊位。

AT89C51是美国ATMEL公司生产的低电压，高性能CMOS8位单片机，片内含4k bytes的可反复擦写的只读程序存储器（PEROM）和128 bytes的随机存取数据存储器（RAM），器件采用ATMEL公司的高密度、非易失性存储技术生产，兼容标准MCS-51指令系统，片内置通用8位中央处理器（CPU）和Flash存储单元，功能强大AT89C51单片机用法可为您提供许多高性价比的应用场合，可灵活科技领域应用于各种支配领域。

AT89C51方框图引脚功能说明·Vcc：电源电压·GND：地·P0 口：P0 口是一组8 位漏极开路型双向I／O 口，也即地址／数据总线复用口。

作为输出口用时，每位能吸收电流的方式驱动8个TTL逻辑门电路，对端口写“1”可作为差阻抗输入端用。

在访问外部数据存储器或程序存储器时，这组口线分时转换地址（低8位）和数据总线复用，在访问期间激活内部上拉电阻。

英文原文DescriptionThe AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash Programmable and Erasable Read Only Memory (PEROM) and 128 bytes RAM. The device is manufactured using Atm-el’s high density nonvolatile memory technology and is compatible with the industry standard MCS-51™instruction set and pin out. The chip combines a versatile 8-bit CPU with Flash on a monolithic chip, the Atm-el AT89C51 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications.Features:• Compatible with MCS-51™ Products• 4K Bytes of In-System Reprogrammable Flash Memory• Endurance: 1,000 Write/Erase Cycles• Fully Static Operation: 0 Hz to 24 MHz• Three-Level Program Memory Lock• 128 x 8-Bit Internal RAM• 32 Programmable I/O Lines• Two 16-Bit Timer/Counters• Six Interrupt Sources• Programmable Serial Channel• Low Power Idle and Power Down ModesThe AT89C51 provides the following standard features: 4K bytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator and clock circuitry. In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port and interrupt system to continue functioning. The Power Down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset.Block DiagramPin Description:VCC Supply voltage.GND Ground.Port 0Port 0 is an 8-bit open drain bidirectional I/O port. As an output port each pin can sink eight TTL inputs. When is are written to port 0 pins, the pins can be used as high impedance inputs.Port 0 may also be configured to be the multiplexed low-order address/data bus during accesses to external program and data memory. In this mode P0 has internal pull-ups.Port 0 also receives the code bytes during Flash programming, and outputs the code bytes during program verification. External pull-ups are required during program verification.Port 1Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1 output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pull-ups.Port 1 also receives the low-order address bytes during Flash programming and verification.Port 2Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2 output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pull-ups.Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses (MOVX @ DPTR). In this application it uses strong internal pull-ups when emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register.Port 2 also receives the high-order address bits and some control signals during Flash programming and verification.Port 3Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3 output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pull-ups.Port 3 also serves the functions of various special features of the AT89C51 as listed below:Port 3 alsoreceives some controlsignals for Flashprogramming andverification.RSTReset input. Ahigh on this pin fortwo machine cycles while the oscillator is running resets the device.ALE/PROGAddress Latch Enable output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG) during Flash programming.In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency, and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped during each access to external Data Memory.If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the micro-controller is in external execution mode.PSENProgram Store Enable is the read strobe to external program memory.When the AT89C51 is executing code from external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory.EA/VPPExternal Access Enable. EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset.EA should be strapped to VCC for internal program executions.This pin also receives the 12-volt programming enable voltage(VPP) during Flash programming, for parts that require 12-volt VPP.XTAL1Input to the inverting oscillator amplifier and input to the internal clock operating circuit.XTAL2Output from the inverting oscillator amplifier.Oscillator CharacteristicsXTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier which can be configured for use as an on-chip oscillator, as shown in Figure 1. Either a quartz crystal or ceramic resonator may be used. To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 is driven as shown in Figure 2. There are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high and low time specifications must be observed.Idle ModeIn idle mode, the CPU puts itself to sleep while all the on-chip peripherals remain active. The mode is invoked by software. The content of the on-chip RAM and all the special functions registers remain unchanged during this mode. The idle mode can be terminated by any enabled interrupt or by a hardware reset.It should be noted that when idle is terminated by a hard ware reset, the device normally resumes program execution, from where it left off, up to two machine cycles before the internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this event, but access to the port pins is not inhibited. To eliminate the possibility of an unexpected write to a port pin when Idle is terminated by reset, the instruction following the one that invokes Idle should not be one that writes to a port pin or to external memory.mode Program memory ALE ^pens Port0 Port1Port2Port3idle internal 11 data data data DataIdle External 11 floatData data DataIn the power down mode the oscillator is stopped, and the instruction that invokes power down is the last instruction executed. The on-chip RAM and Special Function Registers retain their values until the power down mode is terminated. The only exit from power down is a hardware reset. Reset redefines the SF-Rs but does not change the on-chip RAM. The reset should not be activated before VCC is restored to its normal operating level and must be held active long enough to allow the oscillator to restart and stabilize.Program Memory Lock BitsOn the chip are three lock bits which can be left unprogrammed (U) or can be programmed (P) to obtain the additional features listed in the table below:and latched during reset. If the device is powered up without a reset, the latch initializes to a random value, and holds that value until reset is activated. It is necessary that the latched value of EA be in agreement with the current logic level at that pin in order for the device to function properly.– Reserved bits.. Reset value depends on reset source.中文原文描述AT89C51是美国ATMEL公司生产的低电压，高性能CMOS8位单片机，片内含4Kbytes的快速可擦写的只读程序存储器（PEROM）和128 bytes 的随机存取数据存储器（RAM），器件采用ATMEL公司的高密度、非易失性存储技术生产，兼容标准MCS-51产品指令系统，片内置通用8位中央处理器（CPU）和flesh存储单元，功能强大AT89C51单片机可为您提供许多高性价比的应用场合，可灵活应用于各种控制领域。

AT89C51DescriptionThe AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash Programmable and Erasable Read Only Memory (PEROM). The device is manufactured using Atmel’s high density nonvolatile memory technology and is compatible with the industry standard MCS-51™ instruction-set and pinout. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications.Features•Compatible with MCS-51™ Products•4K Bytes of In-System Reprogrammable Flash Memory–Endurance: 1,000 Write/Erase Cycles•Fully Static Operation: 0 Hz to 24 MHz•Three-Level Program Memory Lock•128 x 8-Bit Internal RAM•32 Programmable I/O Lines•Two 16-Bit Timer/Counters•Six Interrupt Sources•Programmable Serial Channel•Low Power Idle and Power Down ModesThe A T89C51 provides the following standard features: 4K bytes of Flash,128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator and clock circuitry. In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port and interrupt system to continue functioning. The Power-down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset.VCCSupply voltage.GNDGround.Port 0Port 0 is an 8-bit open-drain bi-directional I/O port. As an output port, each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high-impedance inputs.Port 0 may also be configured to be the multiplexed low-order address/data bus during accesses to external program and data memory. In this mode P0 has internal pullups.Port 0 also receives the code bytes during Flash programming, and outputs the code bytes during program verification. External pullups are required during program verification.Port 1Port 1 is an 8-bit bi-directional I/O port with internal pullups.The Port 1 output buffers can sink/source four TTL inputs.When 1s are written to Port 1 pins they are pulled high by the internal pullups and can be used as inputs. As inputs,Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pullups.Port 1 also receives the low-order address bytes during Flash programming and verification.Port 2Port 2 is an 8-bit bi-directional I/O port with internal pullups.The Port 2 output buffers can sink/source four TTL inputs.When 1s are written to Port 2 pins they are pulled high by the internal pullups and can be used as inputs. As inputs,Port 2 pins that are externally being pulled low willsource current (IIL) because of the internal pullups.Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses (MOVX @DPTR). In this application, it uses strong internal pullups when emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register. Port 2 also receives the high-order address bits and some control signals during Flash programming and verification.Port 3Port 3 is an 8-bit bi-directional I/O port with internal pullups. The Port 3 output buffers can sink/source four TTL inputs.When 1s are written to Port 3 pins they are pulled high by the internal pullups and can be used as inputs. As inputs,Port 3 pins that are externally being pulled low will source current (IIL) because of the pullups. Port 3 also serves the functions of various special features of the AT89C51 as listed below:Port 3 also receives some control signals for Flash programming and verification.RSTReset input. A high on this pin for two machine cycles while the oscillator is running resets the device.ALE/PROGAddress Latch Enable output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG) during Flash programming. In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency, and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped during each access to external DataMemory.If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode.PSENProgram Store Enable is the read strobe to external program memory. When the AT89C51 is executing code from external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory.EA/VPPExternal Access Enable. EA must be strapped to GND in order to enable the device to fetch codefrom external program memory locations starting at 0000H up to FFFFH.Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset. EA should be strapped to VCC for internal program executions.This pin also receives the 12-volt programming enable voltage (VPP) during Flash programming, for parts that require 12-volt VPP.XTAL1Input to the inverting oscillator amplifier and input to the internal clock operating circuit.XTAL2Output from the inverting oscillator amplifier.Oscillator CharacteristicsXTAL1 and XTAL2 are the input and output, respectively,of an inverting amplifier which can be configured for use as an on-chip oscillator, as shown in Figure 1. Either a quartz crystal or ceramic resonator may be used. To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 is driven as shown in Figure 2.There are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high and low time specifications must be observed.Idle ModeIn idle mode, the CPU puts itself to sleep while all the on-chip peripherals remain active. The mode is invoked by software. The content of the on-chip RAM and all the special functions registers remain unchanged during this mode. The idle mode can be terminated by any enabled interrupt or by a hardware reset. It should be noted that when idle is terminated by a hard ware reset, the device normally resumes program execution, from where it left off, up to two machine cycles before the internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this event, but access to the port pins is not inhibited. To eliminate the possibility of an unexpected write to a port pin when Idle is terminated by reset, the instruction following the one that invokes Idle should not be one that writes to a port pin or to external memory.Figure 1. Oscillator ConnectionsNote: C1, C2 = 30 pF ± 10 pF for Crystals= 40 pF ± 10 pF for Ceramic ResonatorsFigure 2. External Clock Drive ConfigurationPower-down ModeIn the power-down mode, the oscillator is stopped, and the instruction that invokes power-down is the last instruction executed. The on-chip RAM and Special Function Registers retain their values until the power-down mode is terminated. The only exit from power-down is a hardware reset. Reset redefines the SFRs but does not change the on-chip RAM. The reset should not be activated before VCC is restored to its normal operating level and must be held active long enough to allow the oscillator to restart and stabilize.Program Memory Lock BitsOn the chip are three lock bits which can be left unprogrammed (U) or can be programmed (P) to obtain the additional features listed in the table below.When lock bit 1 is programmed, the logic level at the EA pin is sampled and latched during reset. If the device is powered up without a reset, the latch initializes to a random value, and holds that value until reset is activated. It is necessary that the latched value of EA be in agreement with the current logic level at that pin in order for the device to function properly.Programming the FlashThe AT89C51 is normally shipped with the on-chip Flash memory array in the erased state (that is, contents = FFH)and ready to be programmed. The programming interface accepts either a high-voltage (12-volt) or a low-voltage (VCC) program enable signal. The low-voltage programming mode provides a convenient way to program the AT89C51 inside the user’s system, while the high-voltage programming mode is compatible with conventional thirdparty Flash or EPROM programmers.The AT89C51 is shipped with either the high-voltage or low-voltage programming mode enabled. The respective top-side marking and device signature codes are listed in the following table.The AT89C51 code memory array is programmed byte-by-byte in either programming mode. To program any non-blank byte in the on-chip Flash Memory, the entire memory must be erased using the Chip Erase Mode. Programming Algorithm: Before programming the AT89C51, the address, data and control signals should be set up according to the Flash programming mode table and Figures 3 and 4. To program the AT89C51, take the following steps.1. Input the desired memory location on the address lines.2. Input the appropriate data byte on the data lines.3. Activate the correct combination of control signals.4. Raise EA/VPP to 12V for the high-voltage programming mode.5. Pulse ALE/PROG once to program a byte in the Flash array or the lock bits. The byte-write cycle is self-timedand typically takes no more than 1.5 ms. Repeat steps 1 through 5, changing the address and data for the entire array or until the end of the object file is reached.Data Polling: The A T89C51 features Data Polling to indicate the end of a write cycle. During a write cycle, anattempted read of the last byte written will result in the complement of the written datum on PO.7. Once the write cycle has been completed, true data are valid on all outputs, and the next cycle may begin. Data Polling may begin any time after a write cycle has been initiated.Ready/Busy: The progress of byte programming can also be monitored by the RDY/BSY output signal. P3.4 is pulled low after ALE goes high during programming to indicate BUSY. P3.4 is pulled high again when programming is done to indicate READY.Program Verify: If lock bits LB1 and LB2 have not been programmed, the programmed code data can be read back via the address and data lines for verification. The lock bits cannot be verified directly. Verification of the lock bits is achieved by observing that their features are enabled.Chip Erase: The entire Flash array is erased electrically by using the proper combination of control signals and by holding ALE/PROG low for 10 ms. The code array is written with all “1”s. The chip erase operation must be executed before the code memory can be re-programmed.Reading the Signature Bytes: The signature bytes are read by the same procedure as a normal verification of locations 030H, 031H, and 032H, except that P3.6 and P3.7 must be pulled to a logic low. The values returned are as follows.(030H) = 1EH indicates manufactured by Atmel(031H) = 51H indicates 89C51(032H) = FFH indicates 12V programming(032H) = 05H indicates 5V programmingProgramming InterfaceEvery code byte in the Flash array can be written and the entire array can be erased by using the appropriate combination of control signals. The write operation cycle is selftimed and once initiated, will automatically time itself to completion.All major programming vendors offer worldwide support for the Atmel microcontroller series. Please contact your local programming vendor for the appropriate software revision.Flash Programming and Verification Waveforms - High-voltage Mode (VPP = 12V)Flash Programming and Verification Waveforms - Low-voltage Mode (VPP = 5V)Flash Programming and Verification Characteristics TA = 0°C to 70°C, VCC = 5.0 ± 10%Absolute Maximum Ratings**NOTICE: Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periodsmay affect device reliability.DC CharacteristicsTA = -40°C to 85°C, VCC = 5.0V ±20% (unless otherwise noted)Notes: 1. Under steady state (non-transient) conditions, IOL must be externally limited as follows: Maximum IOL per port pin: 10 mAMaximum IOL per 8-bit port: Port 0: 26 mAPorts 1, 2, 3: 15 mAMaximum total IOL for all output pins: 71 mAIf IOL exceeds the test condition, VOL may exceed the related specification. Pins are not guaranteed to sink current greater than the listed test conditions.2. Minimum VCC for Power-down is 2V.AC CharacteristicsUnder operating conditions, load capacitance for Port 0, ALE/PROG, and PSEN = 100 pF; load capacitance for all other outputs = 80 pF.External Program and Data Memory CharacteristicsExternal Program Memory Read CycleExternal Data Memory Read CycleExternal Data Memory Write CycleExternal Clock Drive WaveformsExternal Clock DriveSerial Port Timing: Shift Register Mode Test Conditions(VCC = 5.0 V ±20%; Load Capacitance = 80 pF)Shift Register Mode Timing WaveformsAC Testing Input/Output Waveforms(1)Note: 1. AC Inputs during testing are driven at VCC - 0.5V for a logic 1 and 0.45V for a logic 0. Timing measurements are made at VIH min. for a logic 1 and VIL max. for a logic 0.Float Waveforms(1)Note: 1. For timing purposes, a port pin is no longer floating when a 100mV change from load voltage occurs. A port pin begins to float when 100mV change from the loaded VOH/VOL level occurs.。

The Introduction of AT 89C51 DescriptionMicrocontrollers are used in a multitude of commercial applications such as modems, motor-control systems, air conditioner control systems, automotive engine and among others. The high processing speed and enhanced peripheral set of these microcontrollers make them suitable for such high-speed event-based applications. However, these critical application domains also require that these microcontrollers are highly reliable. The high reliability and low market risks can be ensured by a robust testing process and a proper tools environment for the validation of these microcontrollers both at the component and at the system level. The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash programmable and erasable read only memory (PEROM). The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry-standard MCS-51 instruction set. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides a highly-flexible and cost-effective solution to many embedded control applications.Function characteristicThe AT89C51 provides the following standard features: 4K bytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, one five vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator and clock circuitry. In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port and interrupt system tocontinue functioning. The Power-down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset.Pin Description·VCC: Supply voltage.·GND: Ground.·Port 0: Port 0 is an 8-bit open-drain bi-directional I/O port. As an output port, each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high impedance inputs. Port 0 may also be configured to be the multiplexed low order address/data bus during accesses to external program and data memory. In this mode P0 has internal pull ups. Port 0 also receives the code bytes during Flash programming, and outputs the code bytes during program verification. External pull ups are required during program verification.·Port 1: Port 1 is an 8-bit bi-directional I/O port with internal pull ups. The Port 1 output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled high by the internal pull ups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pull ups. Port 1 also receives the low-order address bytes during Flash programming and verification.·Port 2: Port 2 is an 8-bit bi-directional I/O port with internal pull ups. The Port 2 output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins they are pulled high by the internal pull ups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pull ups. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pull ups. Port 2 emits the high-order address byte during fetches from external program memory andduring accesses to external data memory that uses 16-bit addresses (MOVX@DPTR). In this application, it uses strong internal pull-ups when emitting 1s. During accesses to external data memory that uses 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register. Port 2 also receives the high-order address bits and some control signals during Flash programming and verification.·Port 3: Port 3 is an 8-bit bi-directional I/O port with internal pull ups. The Port 3 output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins they are pulled high by the internal pull ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pull ups.Port 3 also serves the functions of various special features of the AT89C51 as listed below。

The Introduction of AT 89C51DescriptionThe AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash programmable and erasable read only memory (PEROM). The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry-standard MCS-51 instruction set and pinout. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides a highly-flexible and cost-effective solution to many embedded control applications. Function characteristicThe AT89C51 provides the following standard features: 4K bytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator and clock circuitry. In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port and interrupt system to continue functioning. The Power-down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset.Pin DescriptionVCC：Supply voltage.GND：Ground.Port 0：Port 0 is an 8-bit open-drain bi-directional I/O port. As an output port, each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used ashighimpedance inputs. Port 0 may also be configured to be the multiplexed loworder address/data bus during accesses to external program and data memory. In this mode P0 has internal pullups. Port 0 also receives the code bytes during Flash programming, and outputs the code bytes during program verification. External pullups are required during program verification.Port 1Port 1 is an 8-bit bi-directional I/O port with internal pullups. The Port 1 output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled high by the internal pullups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pullups. Port 1 also receives the low-order address bytes during Flash programming and verification.Port 2Port 2 is an 8-bit bi-directional I/O port with internal pullups. The Port 2 output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins they are pulled high by the internal pullups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current, because of the internal pullups. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses. In this application, it uses strong internal pullupswhen emitting 1s. During accesses to external data memory that use 8-bit addresses, Port 2 emits the contents of the P2 Special Function Register. Port 2 also receives the high-order address bits and some control signals during Flash programming and verification.Port 3Port 3 is an 8-bit bi-directional I/O port with internal pullups. The Port 3 output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins they are pulled high by the internal pullups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pullups. Port 3 also- 2 -serves the functions of variousspecial features of the AT89C51 as listed below:RSTReset input. A high on this pin for two machine cycles while the oscillator is running resets the device.ALE/PROGAddress Latch Enable output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG) during Flash programming. In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency, and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped during each access to external Data Memory.If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode.PSENProgram Store Enable is the read strobe to external program memory. When theAT89C51 is executing code from external program memory, PSEN is activated twice each- 3 -machine cycle, except that two PSEN activations are skipped during each access to external data memory.EA/VPPExternal Access Enable. EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset.EA should be strapped to VCC for internal program executions. This pin also receives the 12-volt programming enable voltage(VPP) during Flash programming, for parts that require12-volt VPP.XTAL1Input to the inverting oscillator amplifier and input to the internal clock operating circuit.XTAL2Out put from the inverting oscillator amplifier.Oscillator CharacteristicsXTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier which can be configured for use as an on-chip oscillator, as shown in Figure 1.Either a quartz crystal or ceramic resonator may be used. To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 is driven as shown in Figure 2.There are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high and low time specifications must be observed.- 4 -- 5 -Figure 1. Oscillator Connections Figure 2. External Clock Drive ConfigurationIdle ModeIn idle mode, the CPU puts itself to sleep while all the onchip peripherals remain active. The mode is invoked by software. The content of the on-chip RAM and all the special functions registers remain unchanged during this mode. The idle mode can be terminated by any enabled interrupt or by a hardware reset. It should be noted that when idle is terminated by a hard ware reset, the device normally resumes program execution, from where it left off, up to two machine cycles before the internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this event, but access to the port pins is not inhibited. To eliminate the possibility of an unexpected write to a port pin when Idle is terminated by reset, the instruction following the one that invokes Idle should not be one that writes to a port pin or to external memory.Power-down ModeIn the power-down mode, the oscillator is stopped, and the instruction that invokes power-down is the last instruction executed. The on-chip RAM and Special Function- 6 -Registers retain their values until the power-down mode is terminated. The only exit from power-down is a hardware reset. Reset redefines the SFRs but does not change the on-chip RAM. The reset should not be activated before VCC is restored to its normal operatinglevel and must be held active long enough to allow the oscillator to restart and stabilize.Program Memory Lock BitsOn the chip are three lock bits which can be left unprogrammed (U) or can beprogrammed (P) to obtain the additional features listed in the table below.When lock bit 1 is programmed, the logic level at the EA pin is sampled and latched during reset. If the device is powered up without a reset, the latch initializes to a random value, and holds that value until reset is activated. It is necessary that the latched value of EA be in agreement with the current logic level at that pin in order for the device to function properly.Programming the FlashThe AT89C51 is normally shipped with the on-chip Flash memory array in the erased state (that is, contents = FFH)and ready to be programmed. The programming interface accepts either a high-voltage (12-volt) or a low-voltage(VCC) program enable signal. Thelow-voltage programming mode provides a convenient way to program theAT89C51 inside the user’s system, while the high-voltage programming mode is compatible with conventional third party Flash or EPROM programmers. The AT89C51 is shipped with either the high-voltage or low-voltage programming mode enabled. The respective top-side marking and device signature codes are listed in the following table.The AT89C51 code memory array is programmed byte-bybyte in either programming mode. To program any nonblank byte in the on-chip Flash Memory, the entire memory must be erased using the Chip Erase Mode.Programming Algorithm: Before programming theAT89C51, the address, data and control signals should beset up according to the Flash programming mode table. To program the AT89C51, take the following steps.1. Input the desired memory location on the address lines.2. Input the appropriate data byte on the data lines.3. Activate the correct combination of control signals.4. Raise EA/VPP to 12V for the high-voltage programming mode.5. Pulse ALE/PROG once to program a byte in the Flash array or the lock bits. The byte-write cycle is self-timed and typically takes no more than 1.5 ms. Repeat steps 1 through 5, changing the address and data for the entire array or until the end of the object file is reached.Data Polling: The AT89C51 features Data Polling to indicate the end of a write cycle. During a write cycle, an attempted read of the last byte written will result in the complement of the written datum on PO.7. Once the write cycle has been completed, true data are valid on all outputs, and the next cycle may begin. Data Polling may begin any time after a write cycle has been initiated.Ready/Busy: The progress of byte programming can also be monitored by the RDY/BSY output signal. P3.4 is pulled low after ALE goes high during programming to indicate BUSY. P3.4 is pulled high again when programming is done to indicate READY.- 7 -Program Verify:If lock bits LB1 and LB2 have not been programmed, the programmed code data can be read back via the address and data lines for verification. The lock bits cannot be verified directly. Verification of the lock bits is achieved by observing that their features are enabled.Chip Erase: The entire Flash array is erased electrically by using the proper combination of control signals and by holding ALE/PROG low for 10 ms. The code array is written with all “1”s. The chip erase operation must be executed before the code memory can be re-programmed.Reading the Signature Bytes:The sign ature bytes are read by the same procedure as a normal verification of locations 030H, 031H, and 032H, except that P3.6 andP3.7 must be pulled to a logic low. The values returned are as follows.(030H) = 1EH indicates manufactured by Atmel(031H) = 51H indicates 89C51(032H) = FFH indicates 12V programming(032H) = 05H indicates 5V programmingProgramming InterfaceEvery code byte in the Flash array can be written and the entire array can be erased by using the appropriate combination of control signals. The write operation cycle is self timed and once initiated, will automatically time itself to completion. All major programming vendors offer worldwide support for the Atmel microcontroller series. Please contact your local programming vendor for the appropriate software revision.- 8 -AT89C51的介绍述AT89C51是一个 电压，高性能CMOS8 单片机带有4K 节的 复擦写的程序 储器 PENROM 和128 节的 数据 储器 RAM ， 种器件采用ATMEL公 的高密度 容易丢失 储技术生产，并 能够 MCS-51系列的单片- 9 -机兼容 片内含有8 中央处理器和闪烁 储单元，有较强的 能的AT89C51单片机能够被 用到 制领域中能特性AT89C51提供 的 能标准：4K 节闪烁 储器，128 节随机 数据 储器，32个I/O口，2个16 定时/计数器，1个5向 级中断结构，1个串行通信口，片内震荡器和时钟电路 另外，AT89C51 进行0HZ的静态逻辑操作，并支持 种 件的节电模式 闲散方式停 中央处理器的工作，能够允许随机 数据 储器 定时/计数器 串行通信口及中断系统继续工作 掉电方式保 随机 数据 储器中的内容，但震荡器停 工作并禁 其它所有部件的工作直到 一个复引脚 述VCC：电源电压GND：地P0口：P0口是一组8 漏极开路 向I/O口，即地址/数据总线复用口 作为输出口时， 一个管脚都能够驱动8个TTL电路 当“1”被写入P0口时， 个管脚都能够作为高阻抗输入端 P0口 能够在 问外部数据 储器或程序 储器时，转换地址和数据总线复用，并在 时激活内部的 拉电阻 P0口在闪烁编程时，P0口接收指 ，在程序校验时，输出指 ，需要接电阻P1口：P1口一个带内部 拉电阻的8 向I/O口，P1的输出缓冲级 驱动4个TTL 电路 对端口写“1”，通过内部的电阻把端口拉到高电 ， 时 作为输入口 因为内部有电阻，某个引脚被外部信 拉 时输出一个电流 闪烁编程时和程序校验时，P1口接收 8 地址P2口：- 10 -P2口是一个内部带有 拉电阻的8 向I/O口，P2的输出缓冲级 驱动4个TTL电路 对端口写“1”，通过内部的电阻把端口拉到高电 ， 时， 作为输入口 因为内部有电阻，某个引脚被外部信 拉 时会输出一个电流 在 问外部程序 储器或16 地址的外部数据 储器时，P2口 出高8 地址数据 在 问8 地址的外部数据 储器时，P2口线 的内容在整个运行期间 闪烁编程或校验时，P2口接收高 地址和其它 制信P3口：P3口是一组带有内部电阻的8 向I/O口，P3口输出缓冲故 驱动4个TTL 电路 对P3口写如“1”时，它们被内部电阻拉到高电 并 作为输入端时，被外部拉 的P3口将用电阻输出电流P3口除了作为一般的I/O口外，更重要的用途是它的第 能，如 表所示：端口引脚第 能P3.0 RXDP3.1 TXDP3.2 INT0P3.3 INT1P3.4 T0P3.5 T1P3.6 WRP3.7 RDP3口 接收一些用于闪烁 储器编程和程序校验的 制信RST：复 输入 当震荡器工作时，RET引脚出现 个机器周期 的高电 将使单片机复ALE/PROG：当 问外部程序 储器或数据 储器时，ALE输出脉冲用于锁 地址的 8 节 即使 问外部 储器，ALE 时钟震荡频率的1/16输出固定的 脉冲信 ，因 它 对输出时钟或用于定时目的 要注意的是： 当 问外部数据 储器时将跳过一个ALE脉冲时，闪烁 储器编程时， 个引脚 用于输入编程脉冲 如果 要， 对特殊寄 器区中的8EH单元的D0 置禁 ALE操作 个 置 只有一条MOVX和MOVC指 ALE才会被 用 外， 个引脚会微弱拉高，单片机执行外部程序时， 置ALE无效PSEN：程序储 允许输出是外部程序 储器的读选通信 ，当AT89C51由外部程序 储器读 指 时， 个机器周期 次PSEN 有效，即输出 个脉冲 在 期间，当 问外部数据 储器时， 次有效的PSEN 信 出现EA/VPP：外部 问允许 欲使中央处理器仅 问外部程序 储器，EA端 须保持 电 需要注意的是：如果 密 LBI被编程，复 时内部会锁 EA端状态 如EA端为高电 ，CPU则执行内部程序 储器中的指 闪烁 储器编程时，该引脚 +12V 的编程允许电压VPP，当然 须是该器件是使用12V编程电压VPPXTAL1：震荡器 相放大器及内部时钟发生器的输入端XTAL2：震荡器 相放大器的输出端时钟震荡器AT89C51中有一个用于构 内部震荡器的高增益 相放大器，引脚XTAL1和XTAL2 别是该放大器的输入端和输出端 个放大器 作为 馈元件的片外石英晶体或陶瓷谐振器一起构 自然震荡器 外接石英晶体及电容C1，C2接在放大器的 馈回路中构 并联震荡电路 对外接电容C1，C2虽然没有十 格的要求，但电容容 的大小会轻微影响震荡频率的高 震荡器工作的稳定性 起振的难易程序及温度稳定性 如果使用石英晶体， 们 荐电容使用30PF±10PF，而如果使用陶瓷振荡器建议选择40PF±10PF 用户也 采用外部时钟 采用外部时钟的电路如图示 种情况 ，外部时钟脉冲接到XTAL1端，即内部时钟发生器的输入端，XTAL2则悬空 由于外部时钟信 是通过一个2 频触发器 作为内部时钟信 的，所 对外部时钟信 的占空比没有特殊要求，但最小高电 持续时间和最大的 电 持续时间 符合产品技术条件的要求内部振荡电路外部振荡电路闲散节电模式AT89C51有 种 用 件编程的省电模式，它们是闲散模式和掉电工作模式 种方式是 制 用寄 器PCON中的PD和IDL 来实现的 PD是掉电模式，当PD=1时，激活掉电工作模式，单片机进入掉电工作状态 IDL是闲散等待方式，当IDL=1，激活闲散工作状态，单片机进入睡 状态 如需要 时进入 种工作模式，即PD和IDL 时为1，则先激活掉电模式 在闲散工作模式状态，中央处理器CPU 保持睡 状态，而所有片内的外 保持激活状态， 种方式由 件产生 时，片内随机 数据 储器和所有特殊 能寄 器的内容保持 闲散模式 由任何允许的中断请求或硬件复 终 终 闲散工作模式的方法有 种，一是任何一条被允许中断的 件被激活，IDL被硬件清除，即刻终 闲散工作模式 程序会首先影响中断，进入中断服 程序，执行完中断服 程序，并紧随RETI指 ， 一条要执行的指 就是使单片机进入闲散工作模式，那条指 面的一条指 是通过硬件复 也 将闲散工作模式终 需要注意的是：当由硬件复 来终 闲散工作模式时，中央处理器CPU通常是 激活空闲模式那条指 的 一条开始继续执行程序的，要完 内部复 操作，硬件复 脉冲要保持 个机器周期有效，在 种情况 ，内部禁中央处理器CPU 问片内RAM，而允许 问其他端口，为了避免 能对端口产生的意外写入：激活闲散模式的那条指 面的一条指 是一条对端口或外部 储器的写入指掉电模式在掉电模式 ，振荡器停 工作，进入掉电模式的指 是最 一条被执行的指 ，片内RAM和特殊 能寄 器的内容在中指掉电模式前被冻结 出掉电模式的唯一方法是硬件复 ，复 将 新定义全部特殊 能寄 器但 改 RAM中的内容，在VCC恢复到 常工作电 前，复 无效 须保持一定时间 使振荡器 新启动并稳定工作闲散和掉电模式外部引脚状态程序 储器的 密AT89C51 使用对芯片 的 个 密 LB1，LB2，LB3进行编程 P 或 编程 U 得到如 表所示的 能：程序 密 保护类型1 U U U 没有程序保护 能2 P U U 禁 外部程序 储器中执行MOVC指 读 内部程序 储器的内容3 P P U 除 表 能外， 禁 程序校验4 P P P 除 能外， 时禁 外部执行当LB1被编程时，在复 期间，EA端的电 被锁 ，如果单片机 电 一直没有复 ，锁 起来的初始值是一个 确定数， 个 确定数会一直保 到 复 置 为了使单片机 常工作，被锁 的EA电 个引脚当前辑电 一 机密 只能通过整片擦除的方法清除编程的F真且shF真且sh通常是在AT89C51的出货 片 闪 内 阵列中删除状态 即内容=快跳频 并随时准备进行编程 编程接口 接 一个高电压 12伏 或 电压 虚拟通道连接 计划使信 .在 电压编程模式提供了一个方便的方法的程序AT89C51单片机在用户的系统，而高电压编程模式是符合常规的第 方Flash或 擦写 编程只读 储器程序员 该AT89C51单片机随 无论是高电压或 电压编程模式 AT89C51单片机 码的编程 储器阵列 节在 种编程模式 编程任何nonblank 节的片 闪 ，整个记 体 须清除使用芯片擦除模式规划算法：在编程AT89C51单片机，地址，数据和 制信 立 据Flash编程模式表 到程序的AT89C51单片机，采 面的 骤1 输入所需的内 置的地址线2 输入相 的数据 节的数据线3 激活的 确组合的 制信4 提高电子艺界/ VPP 12V的高电压编程模式5 脉冲进修/孕酮一次计划中的一个 节闪 阵列或锁定 节写周期自 通常需要的时间和 超过1.5毫秒 重复 骤1到5 ，更改地址和数据为整个阵列或到 ，对象文件达 共识数据 询：该AT89C51的数据 询 能说明结束了写周期 在写周期，一个试图读 最 节书面将导 补充书面资料 PO.7 一旦写周期已 完 ， 的数据是有效的所有输出， 一个周期开始 数据 询 开始任何时候在写周期已 开始 准备/忙：进展 节编程也 被监测的RDY /天空电视 的输出信 P3.4被拉高进修 用编程期间说明忙碌的 P3.4被拉高时再次编程 做表明准备程序验证：如果锁定 LB1和LB2尚未编程，编程 码 读 数据备份通过地址和数据线进行 查 锁定 无法验证直接 验证锁 是所 得的观测，其 能已启用 芯片擦除：整个闪 阵列抹去电通过 当的组合和 制信 举 进修/孕酮 了10毫秒 数组的 码写入 所有“ 1 ” 该芯片擦除操作 须得到执行之前的 码 储器 重新编程读 节的签 ：签 节宣读了相 的程序作为一个 常的 查工作地点030H ，031H ，并032H ，但P3.6和P3.7 须 出一个逻辑 返回的值是如030H = 1EH表明制造商031H = 51H表明基于89C51032H =快跳频表明12V的编程032H = 05H显示5V的编程编程接口一个 节的 码在闪 阵列 书面和整个阵列 被删除，使用 当的组合的 制信 写入操作周期一旦启动，将自动时间本身完。

89C51 Microcontroller IntroductionMicrocontrollers are used in a multitude of commercial applications such as modems, motor-control systems, air conditioner control systems automotive engine and among others. The high processing speed and enhaneed peripheral set of these microcontrollers make them suitable for such high-speed event-based applications. However, these critical application domains also require that these microcontrollers are highly reliable. The high reliability and low market risks can be ensured by a robust testing process and a proper tools en vironment for the validation of these microcontrollers both at the comp on ent and at the system level. Intel Plaform Engineering department developed an object-onented multi-threaded test environment for the validation of its AT89C51 automotive microcontrollers・ The goals of this environment was not only to provide a robust testing environment for the AT89C51 automotive microcontrollers but to develop an environment which can be easily extended and reused for the validation of several other future microcontrollers・ The environment was developed in conjunct!on with Microsoft Foundation Classes (AT89C51). The paper describes the design and mechanism of this test environme nt, its interactions with various h a rd wa re/softwa re en vironme ntal components and how to use AT89C51 ・Are 8-bit microcontroller early or 4 bits. One of the most successful is the INTEL 8031, for a simple, reliable and good performanee was a lot of praise. Then developed in 8031 out of MCS51 MCU Systems. SCM systems based on this system until now is still widely used. With the increased requirements of industrial control field, began a 16-bit microcontroller but not ideal because the cost has not been very widely used・After 90 years with the great development of consumer electronics, microcontroller tech no logy has been a huge increase. With INTEL i960 series especially the later series of widely used ARM, 32-bit microcontroller quickly replace high-end 16-bit MCU status and enter the mainstream market. The traditional8-bit microcontroller performance have been the rapid increase capacity in crease compared to 80 the number of times. Curre ntly, high-e nd 32-bit microcontroller clocked over 300MHz z the performa nee catchi ng the mid-90s dedicated processor, while the average model prices fall to one . dollar, the most high-end model is only 10 dollars ・ Modern SCM systems are no Ion ger only in the development and use of bare metal environment, a large number of proprietary embedded operating system is widely used in the full range of SCM・The handheld computers and cell phones as the core processing of high-end microcontroller can even use a dedicated Windows and Linux operating systems.SCM relies on the program, and can be modified・Through different procedures to achieve different functions, in particular special unique features, this is another device much effort needs to be done, some are great efforts are very difficult to achieve. A not very complex functions if the 50's with the United States developed 74 series, or the 60's CD4000 series of these pure hardware buttoned, then the circuit must be a large PCB board! But if the United States if the 70's with a series of successful SCM market, the result will be a drastic change! Just because you are prepared by microcomputer programs can achieve high intelligence, high efficiency and high reliability!IntroductionThe 8-bit AT89C51 CHMOS microcontrollers are designed to handle high-speed calculations and fast input/output operations・ MCS 51 microcontrollers are typically used for high-speed event control systems. Commercial applications in elude modems, motor-control systems printers, photocopiers, air conditioner control systems, disk drives；and medical instruments. The automotive industry use MCS 51 microcontrollers in engine-control systems, airbags, suspension system® and antilock braking systems (ABS). The AT89C51 is especially well suited to applications that benefit from its processing speed and enhanced on-chip peripheral functions set, such as automotive power-train control vehicle dynamic suspension, antilock braking z and stability control applications. Because of these critical applications the market requires a reliable cost-effective controller with a low interrupt latency response, ability to service the high number of time and event driven integrated peripherals needed in real time applications, and a CPU with above average processing power in a single package・ The financial and legal risk of having devices that operate unpredictably is very high. Once in the market, particularly in mission critical applications such as an autopilot or anti-lock braking system, mistakes are financiallyprohibitive. Redesign costs can 「un as high as a $500« much more if the fix means back annotating it across a product family that share the same core and/or peripheral design flaw.I n additi on, field replacements of comp on ents is extremely expe nsive. as the devices are typically sealed in modules with a total value several times that of the component To mitigate these problems, it is essential that comprehensive testing of the controllers be carried out at both the comp orient level and system level un der worst case environmentai and voltage complete and thorough validation necessitates not only a well-defined process but also a proper environment and tools to facilitate and execute the mission successfully・Intel Chandler Platform Engineering group provides postsilicon system validation (SV) of various micro-controllers and processors. The system validation process can be broken into three major type of the device and its application requirements determine which types of testing are performed on the device・The AT89C51 provides the following standard features: 4Kbytes of Flash, 128 bytes of RAM, 32 I/O lines f two 16-bittimer/counters； a five vector two-level interrupt architecture^ full duple ser -ial port, on-chip oscillator and clock addition z the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable powersaving modes. The Idle Mode stops the CPU while allowing the RAM, timer/countersserial port and interrupt sys -tern to continue functioning. The Power-down Mode saves the RAM contents but freezes the oscil -lator disabling all other chip functions until the next hardware reset.Pin DescriptionVCC Supply voltage・GND Ground.Port 0Port 0 is an 8-bit open-drain bi-directional I/O port. As an output port, each pin can sink eight TTL inputs. When Is are written to port 0 pins, the pins can be used as highimpedance in puts ・Port 0 may also be con figured to be the multiplexed loworder address/data bus during accesses to external program and data memory・ In this mode PO has internal pullups ・Port 0 also receives the code bytes during Flash programming’and outputs the code bytes during program verification. External pullups are required during program verificatio n.Port 1Port 1 is an 8-bit bi-directional I/O port with internal Port 1 output buffers can sink/so -urce four TTL Is are written to Port 1 pins they are pulled high by the internal pullups and can be used as in puts ・ As in puts, Port 1 pins that are externally being pulled low will source current (HL) because of the internal pullups・Port 1 also receives the low-order address bytes during Flash programming and verificatio n.Port 2Port 2 is an 8-bit bi-directional I/O port with internal pullups.The Port 2 output buffers can sink/source four TTL Is are written to Port 2 pins they are pulled high by the in ter nal pullups and can be used as inputs. As in puts, Port 2 pins that are exter nally being pulled low will source current (IIL) because of the internal pullups・Port 2 emits the high-order address byte during fetches from external program memory and during accesses to Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pullups・Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses (MOVX @DPTR). In this application/ it uses strong internal pull-ups when emitting Is. During accesses to external data memory that use 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register.Port 2 also receives the high-order address bits and some control signals durin Flash programming and verification.Port 3Port 3 is an 8-bit bi-directional I/O port with internal pullups.The Port 3 output buffers can sink/sou -rce four TTL Is are written to Port 3 pins they are pulled high by the internal pullups and can be used as in puts ・ As inputs.Port 3 pins that are exte「n ally being pulled low will source current (HL) because of the pullups・RSTReset in put A high on this pin for two machi ne cycles while the oscillator is running resets the device.ALE/PROGAddress Latch Enable output pulse for latching the low byte of the address duringaccesses to external memory・This pin is also the program pulse input (PROG) during Flash programming.In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency, and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped duri -ng each access to external desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode・PSENProgram Store Enable is the read strobe to external program memory. When the AT89C51 is executing code from external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory・EA/VPPExternal Access Enable・ EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if lock bit 1 is programmed/ EA will be internally latched on should be strapped to VCC for internal program executions. This pin also receives the 12-volt programming enable voltage (VPP) during Flash programming, for parts that require12-volt VPP.The AT89C51 code memory array is programmed byte-bybyte in either programming mode. To program any nonblank byte in the on-chip Flash Memory, the entire memory must be erased using the Chip Erase Mode.Data Polling: The AT89C51 features Data Polling to indicate the end of a write cycle. During a write cycle, an attempted read of the last byte written will result in the complementof the written datum on ・ Once the write cycle has been completed, true data are valid on all outputs andthe next cycle may begin. Data Polling may begin any time after a write cycle has been initiated・Ready/Busy: The progress of byte programming can also be monitored by the RDY/BSY output signal, is pulled low after ALE goes high during programming to indicate BUSY. is pulled high again when programming is done to indicate READY・Program Verify: If lock bits LB1 and LB2 have not been programmed, the programmed code data can be read back via the address and data lines for verification. The lock bits cannot be verified directly・ Verification of the lock bits is achieved by observing that their features are enabled.A microcomputer interface converts information between two forms. Outside the microcomputer the info rmation han died by an electronic system exists as a physical signal, but within the program/ it is represented nu merically ・ The fun ctio n of any in terface can be broken down into a number of operations which modify the data in some way, so that the process of conversion between the external and internal forms is carried out in a number of steps・An analog-to-digital converter(ADC) is used to convert a continuously variable signal toa corresponding digital form which can take any one of a fixed number of possible binary values・ If the output of the transducer does not vary continuously, no ADC is n ecessary .In this case the signal conditi oning section must convert the in coming signal to a form whichcan be connected directly to the next part of the interface, the input/output section of the microcomputer itself.Output in terfaces take a similar form, the obvious differe nee being that here the flow of information is in the opposite direction; it is passed from the program to the outside world. In this case the program may call an output subroutine which supervises the operation of theinterface and performs the scaling numbers which may be needed for a digital-to-analog converter(DAC). This subroutine passes information in turn to an output device which produces a corresponding electrical signal, which could be converted into analog form using a DAC. Finally the signal is conditioned(usually amplified) to a form suitable for operating an actuator.The signals used within microcomputer circuits are almost always too small to be connected directly to the "outside world" and some kind of interface must be used to translate them to a more appropriate form・ The design of section of interface circuits is one of the most important tasks facing the engineer wishing to apply microcomputers. We have seen that in microcomputers information is represented as discrete patterns of bits; this digital form is most useful when the microcomputer is to be connected to equipment which can only be switched on or off, where each bit might represent the state of a switch or actuator.To solve real-world problems, a microcontroller must have more than just a CPU/a program, and a data memory. In addition, it must contain hardware allowing the CPU to access info「mation from the outside world ・ Once the CPU gathers informatio n and processes the data, it must also be able to effect change on some portion of the outside world. These hardware devices, called peripherals, are the CPU' s window to the outside.The most basic form of peripheral available on microcontrollers is the general purpose 170 port. Each of the I/O pins can be used as either an in put or an output The function of each pin is determined by setting or clearing corresponding bits in a corresponding data direction register during the initialization stage of a program. Each output pin may be driven to either a logic one or a logic zero by using CPU instructions to pin may be viewed (or read.) by the CPU using program instructions.Some type of serial unit is included on microcontrollers to allow the CPU to communicatebit-serially with external devices ・ Using a bit serial format in stead of bit-parallel format requires fewer I/O pins to perform the communication function, which makes it less expensive, but slower. Serial transmissions are performed either synchronously or asynchronously・Its applicationsSCM is widely used in instruments and meters, household appliances, medical equipment, aerospace, specialized equipment, intelligent management and process control fields/ roughly divided into the following several areas:SCM has a small size, low power consumption, controlling function, expansion flexibility, the advantages of miniaturization and ease of use, widely used instrument, combining different types of sensors can be realized, such as voltage, power; frequency, humidity temperature, flow, speed z thicknes® angle, length, hardness, elementa- physical pressure measurement. SCM makes use of digital instruments, intelligence, miniaturization, and functionality than the use of more powerful electronic or digital circuits・ Such as precision measuring equipment (power meter, oscilloscope, variousanalytical instrument).89C51单片机简介单片机普遍应用于商业：诸如调制解调器,电动机操纵系统,空调操纵系统,汽车发动机和其他一些领域。

AT89C51的简况The General Situation of AT89C51Chapter 1 The application of AT89C51 Microcontrollers are used in a multitude of commercial applications such as modems, motor-control systems, air conditioner control systems, automotive engine and among others. The high processing speed and enhanced peripheral set of these microcontrollers make them suitable for such high-speed event-based applications. However, these critical application domains also require that these microcontrollers are highly reliable. The high reliability and low market risks can be ensured by a robust testing process and a proper tools environment for the validation of these microcontrollers both at the component and at the system level. Intel Plaform Engineering department developed an object-oriented multi-threaded test environment for the validation of its AT89C51 automotive microcontrollers. The goals of thisenvironment was not only to provide a robust testing environment for the AT89C51 automotive microcontrollers, but to develop an environment which can be easily extended and reused for the validation of several other future microcontrollers. The environment was developed in conjunction with Microsoft Foundation Classes (AT89C51>. The paper describes the design and mechanism of this test environment, its interactions with various hardware/software environmental components, and how to use AT89C51.1.1 IntroductionThe 8-bit AT89C51 CHMOS microcontrollers are designed to handle high-speedcalculations and fast input/output operations. MCS 51 microcontrollers are typically used for high-speed event control systems. Commercial applications include modems,motor-control systems, printers, photocopiers, air conditioner control systems, disk drives,and medical instruments. The automotive industry use MCS 51 microcontrollers in engine-control systems, airbags, suspensionsystems, and antilock braking systems (ABS>. The AT89C51 is especially well suited to applications that benefit from its processing speed and enhanced on-chip peripheral functions set, such as automotive power-train control, vehicle dynamic suspension, antilock braking, and stability control applications. Because of these critical applications, the market requires a reliable cost-effective controller with a low interrupt latency response, ability to service the high number of time and event driven integrated peripherals needed in real time applications, and a CPU with above average processing power in a single package. The financial and legal risk of having devices that operate unpredictably is very high. Once in the market, particularly in mission criticalapplications such as an autopilot or anti-lock braking system, mistakes are financiallyprohibitive. Redesign costs can run as high as a $500K, much more if the fix means 2 back annotating it across a product family that share the same core and/or peripheral design flaw. In addition, field replacements of components is extremely expensive, as the devices are typically sealed in modules with a total value several times that of the component. To mitigate these problems, it is essential that comprehensive testing of the controllers be carried out at both the component level and system level under worst case environmental and voltage conditions.This complete and thorough validation necessitates not only a well-defined process but also a proper environment and tools to facilitate and execute the mission successfully.Intel Chandler Platform Engineering group provides post silicon system validation (SV> of various micro-controllers and processors. The system validation process can be broken into three major parts.The type of the device and its application requirements determine which types of testing are performed on the device.1.2 The AT89C51 provides the following standard features:4Kbytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bittimer/counters, a five vector two-level interrupt architecture,a full duple ser -ial port, on-chip oscillator and clock circuitry.In addition, the AT89C51 is designed with static logic for operationdown to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters,serial port and interrupt sys -tem to continue functioning. The Power-down Mode saves the RAM contents but freezes the oscil –lator disabling all other chip functions until the next hardware reset.Figure 1-2-1Block Diagram1-3Pin DescriptionVCC Supply voltage.GND Ground.Port 0：Port 0 is an 8-bit open-drain bi-directional I/O port. As an output port, each pin cansink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as highimpedance inputs.Port 0 may also be configured to be the multiplexed loworder address/data busduring accesses to external program and data memory. In this mode P0 has internalpullups.Port 0 also receives the codebytes during Flash programming,and outputs the codebytes during program verification. External pullups are required during programverification.Port 1：Port 1 is an 8-bit bi-directional I/O port with internal pullups.The Port 1 output buffers can sink/so -urce four TTL inputs.When 1s are written to Port 1 pins they are pulled high by the internal pullups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL> because of the internal pullups.Port 1 also receives the low-order address bytes during Flash programming and verification.Port 2：Port 2 is an 8-bit bi-directional I/O port with internal pullups.The Port 2 outputbuffers can sink/source four TTL inputs.When 1s are written to Port 2 pins they arepulled high by the internal pullups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current (IIL> because of the internal pullups. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to Port 2 pins that are externally being pulled low will source current (IIL> because of the internal pullups.Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses (MOVX@DPTR>. In this application, it uses strong internal pull-ups when emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX @ RI>, Port 2 emits the contents of the P2 Special Function Register.Port 2 also receives the high-order address bits and some control signals durin Flash programming and verification.Port 3：Port 3 is an 8-bit bi-directional I/O port with internal pullups.The Port 3 outputbuffers can sink/sou -rce four TTL inputs.When 1s are written to Port 3 pins they are pulled high by the internal pullups and can be used as inputs. As inputs,Port 3 pins that are externally being pulled low will source current (IIL> because of the pullups.Port 3 also serves the functions of various special featuresof the AT89C51 as listed below:RST：Reset input. A high on this pin for two machine cycles whilethe oscillator is running resets the device.ALE/PROG：Address Latch Enable output pulse for latching the low byte of the address duringaccesses to external memory.This pin is also the program pulse input (PROG> during Flash programming.In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency,and may be used for external timing or clocking purposes. Note, however, that one ALEpulse is skipped duri -ng each access to external DataMemory.If desired, ALE operationcan be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active onlyduring a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Settingthe ALE-disable bit has no effect if the microcontroller is in external execution mode.PSEN：Program Store Enable is the read strobe to external program memory. When theAT89C51 is executing code from external program memory, PSEN is activated twiceeach machine cycle, except that two PSEN activations are skipped during each access toexternal data memory.EA/VPP：External Access Enable. EA must be strapped to GND in order to enable the deviceto fetch code from external program memory locations starting at 0000H up to FFFFH.Note, however, that if lock bit 1 is programmed, EA will be internally latched onreset.EA should be strapped to VCC for internal program executions. This pin alsreceives the 12-volt programming enable voltage (VPP> during Flash programming, forparts that require 12-volt VPP.XTAL1：Input to the inverting oscillator amplifier and input to the internal clock operatingcircuit.XTAL2：Output from the inverting oscillator amplifier.Oscillator CharacteristicsXTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifierwhich can be configured for use as an on-chip oscillator, as shown in Figure 1. Either aquartz crystal or ceramic resonator may be used. To drive the device from an externalclock source, XTAL2 should be left unconnected while XTAL1 is driven as shown inFigure 2.There are no requirements on the duty cycle of the external clock signal, sincethe input to the internal clocking circuitry is through a divide-by-two flip-flop, butminimumand maximum voltage high and low time specifications must be observed.Idle ModeIn idle mode, the CPU puts itself to sleep while all the onchip peripherals remainactive. The mode is invoked by software. The content of the on-chip RAM and all thespecial functions registers remain unchanged during this mode. The idle mode can beterminated by any enabled interrupt or by a hardware reset. It should be noted that whenidle is terminated by a hard ware reset, the device normally resumes program execution,from where it left off, up to two machine cycles before the internal reset algorithm takescontrol. On-chip hardware inhibits access to internal RAM in this event, but access to theport pins is not inhibited. To eliminate the possibility of an unexpected write to a port pinwhen Idle is terminated by reset, the instruction following the one that invokes Idleshould not be one that writes to a port pin or to external memory.Power-down ModeIn the power-down mode, the oscillator is stopped, and the instruction that invokes power-down is the last instruction executed. The on-chip RAM and Special Function Registers retain their values until the power-down mode is terminated. The only exit from power-down is a hardware reset. Reset redefines the SFRs but does not change the on-chip RAM. The reset should not be activated before VCC is restored to its normal operating level and must be held active long enough to allow the oscillator to restart and stabilize.The AT89C51 code memory array is programmed byte-bybyte in either programming mode. To program any nonblank byte in the on-chip Flash Memory, the entire memory must be erased using the Chip Erase Mode.2 Programming AlgorithmBefore programming the AT89C51, the address, data and control signals should be set up according to the Flash programming mode table and Figure 3 and Figure 4. To program the AT89C51, take the following steps.1. Input the desired memory location on the address lines.2. Input the appropriate data byte on the data lines. 3. Activate the correct combination of control signals. 4. Raise EA/VPP to 12V for the high-voltage programming mode. 5. Pulse ALE/PROG once to program a byte in the Flash array or the lock bits. The byte-writecycle is self-timed and typically takes no more than 1.5 ms. Repeat steps 1 through 5, changing the address and data for the entire array or until the end of the object file is reached. Data Polling: The AT89C51 features Data Polling to indicate the end of a write cycle. During a write cycle, an attempted read of the last byte written will result in the complement of the written datum on PO.7. Once the write cycle has been completed, true data are valid on all outputs, and the next cycle may begin. Data Polling may begin any time after a writecycle has been initiated.2.1Ready/Busy:The progress of byte programming can also be monitored by the RDY/BSY output signal. P3.4 is pulled low after ALE goes high during programming to indicate BUSY. P3.4 is pulled high again whenprogramming is done to indicate READY.Program Verify:If lock bits LB1 and LB2 have not been programmed, the programmed code data can be read back via the address and data lines for verification. The lock bits cannot be verified directly. Verification of the lock bits is achieved by observing that their features areenabled.Figure 2-1-1 Programming the Flash Figure 2-2-2 Verifying the Flash2.2 Chip Erase:The entire Flash array is erased electrically by using the propercombination of control signals and by holding ALE/PROG low for 10 ms. The code array is written with all “1”s. The chip erase operation must be executed before the code memory can be re-programmed.2.3 Reading the Signature Bytes:The signature bytes are read by the same procedure as a normal verification of locations 030H, 031H, and 032H, except that P3.6 and P3.7 must be pulled to a logic low. The values returned areasfollows.(030H> = 1EH indicates manufactured by Atmel(031H> = 51H indicates 89C51(032H> = FFH indicates 12V programming(032H> = 05H indicates 5V programming2.4 Programming InterfaceEvery code byte in the Flash array can be written and the entire array can be erased by using the appropriate combination of control signals. The write operation cycle is selftimed and once initiated, will automatically time itself to completion. A microcomputer interface converts information between two forms. Outside the microcomputer the information handled by an electronic system exists as a physical signal, but within the program, it is represented numerically. The function of any interface can be broken down into a number of operations which modify the data in some way, so that the process of conversion between the external and internal forms is carried out in a number of steps. An analog-to-digital converter(ADC> is used to convert a continuously variable signal to a corresponding digital form which can take any one of a fixed number of possible binary values. If the output of the transducer does not vary continuously, no ADC is necessary. In this case the signal conditioning section must convert the incoming signal to a form which can be connected directly to the next part of the interface, the input/output section of the microcomputer itself. Output interfaces take a similar form, the obvious difference being that here the flow of information is in the opposite direction。

AT89C51的概况The General Situation of AT89C51Chapter 1 The application of AT89C51 Microcontrollers are used in a multitude of commercial applications such as modems, motor-control systems, air conditioner control systems, automotive engine and among others. The high processing speed and enhanced peripheral set of these microcontrollers make them suitable for such high-speed event-based applications. However, these critical application domains also require that these microcontrollers are highly reliable. The high reliability and low market risks can be ensured by a robust testing process and a proper tools environment for the validation of these microcontrollers both at the component and at the system level. Intel Plaform Engineering department developed an object-oriented multi-threaded test environment for the validation of its AT89C51 automotive microcontrollers. The goals of thisenvironment was not only to provide a robust testing environment for the AT89C51 automotive microcontrollers, but to develop an environment which can be easily extended and reused for the validation of several other future microcontrollers. The environment was developed in conjunction with Microsoft Foundation Classes (AT89C51). The paper describes the design and mechanism of this test environment, its interactions with various hardware/software environmental components, and how to use AT89C51.1.1 IntroductionThe 8-bit AT89C51 CHMOS microcontrollers are designed to handle high-speedcalculations and fast input/output operations. MCS 51 microcontrollers are typically used for high-speed event control systems. Commercial applications include modems,motor-control systems, printers, photocopiers, air conditioner control systems, disk drives,and medical instruments. The automotive industry use MCS 51 microcontrollers in engine-control systems, airbags, suspension systems, and antilock braking systems (ABS). The AT89C51 is especially well suited to applications that benefit from its processing speed and enhanced on-chipperipheral functions set, such as automotive power-train control, vehicle dynamic suspension, antilock braking, and stability control applications. Because of these critical applications, the market requires a reliable cost-effective controller with a low interrupt latency response, ability to service the high number of time and event driven integrated peripherals needed in real time applications, and a CPU with above average processing power in a single package. The financial and legal risk of having devices that operate unpredictably is very high. Once in the market, particularly in mission criticalapplications such as an autopilot or anti-lock braking system, mistakes are financiallyprohibitive. Redesign costs can run as high as a $500K, much more if the fix means 2 back annotating it across a product family that share the same core and/or peripheral design flaw. In addition, field replacements of components is extremely expensive, as the devices are typically sealed in modules with a total value several times that of the component. To mitigate these problems, it is essential that comprehensive testing of the controllers be carried out at both the component level and system level under worst case environmental and voltage conditions.This complete and thorough validation necessitates not only a well-defined process but also a proper environment and tools to facilitate and execute the mission successfully.Intel Chandler Platform Engineering group provides post silicon system validation (SV) of various micro-controllers and processors. The system validation process can be broken into three major parts.The type of the device and its application requirements determine which types of testing are performed on the device.1.2 The AT89C51 provides the following standard features:4Kbytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bittimer/counters, a five vector two-level interrupt architecture,a full duple ser -ial port, on-chip oscillator and clock circuitry.In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters,serial port and interrupt sys -tem to continue functioning. The Power-down Mode saves the RAM contents but freezes the oscil –lator disabling all otherchip functions until the next hardware reset.Figure 1-2-1Block Diagram 1-3Pin DescriptionVCC Supply voltage.GND Ground.Port 0：Port 0 is an 8-bit open-drain bi-directional I/O port. As an output port, each pin cansink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as highimpedance inputs.Port 0 may also be configured to be the multiplexed loworder address/data busduring accesses to external program and data memory. In this mode P0 has internalpullups.Port 0 also receives the code bytes during Flash programming,and outputs the codebytes during program verification. External pullups are required during programverification.Port 1：Port 1 is an 8-bit bi-directional I/O port with internal pullups.The Port 1 output buffers can sink/so -urce four TTL inputs.When 1s are written to Port 1 pins they are pulled high by the internal pullups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pullups.Port 1 also receives the low-order address bytes during Flash programming and verification.Port 2：Port 2 is an 8-bit bi-directional I/O port with internal pullups.The Port 2 outputbuffers can sink/source four TTL inputs.When 1s are written to Port 2 pins they arepulled high by the internal pullups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pullups. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pullups.Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses (MOVX@DPTR). In this application, it uses strong internal pull-ups when emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register.Port 2 also receives the high-order address bits and some control signals durin Flash programming and verification.Port 3：Port 3 is an 8-bit bi-directional I/O port with internal pullups.The Port 3 outputbuffers can sink/sou -rce four TTL inputs.When 1s are written to Port 3 pins they are pulled high by the internal pullupsand can be used as inputs. As inputs,Port 3 pins that are externally being pulled low will source current (IIL) because of the pullups.Port 3 also serves the functions of various special featuresof the AT89C51 as listed below:RST：Reset input. A high on this pin for two machine cycles while the oscillator is running resets the device.ALE/PROG：Address Latch Enable output pulse for latching the low byte of the address duringaccesses to external memory.This pin is also the program pulse input (PROG) during Flash programming.In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency,and may be used for external timing or clocking purposes. Note, however, that one ALEpulse is skipped duri -ng each access to external DataMemory.If desired, ALE operationcan be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active onlyduring a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Settingthe ALE-disable bit has no effect if the microcontroller is in external execution mode.PSEN：Program Store Enable is the read strobe to external program memory. When theAT89C51 is executing code from external program memory, PSEN is activated twiceeach machine cycle, except that two PSEN activations are skipped during each access toexternal data memory.EA/VPP：External Access Enable. EA must be strapped to GND in order to enable the deviceto fetch code from external program memory locations starting at 0000H up to FFFFH.Note, however, that if lock bit 1 is programmed, EA will be internally latched onreset.EA should be strapped to VCC for internal program executions. This pin alsreceives the 12-volt programming enable voltage (VPP) during Flash programming, forparts that require 12-volt VPP.XTAL1：Input to the inverting oscillator amplifier and input to the internal clock operatingcircuit.XTAL2：Output from the inverting oscillator amplifier.Oscillator CharacteristicsXTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifierwhich can be configured for use as an on-chip oscillator, as shown in Figure 1. Either aquartz crystal or ceramic resonator may be used. To drive the device from an externalclock source, XTAL2 should be left unconnected while XTAL1 is driven as shown in Figure2.There are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high and low time specifications must be observed.Idle Mode In idle mode, the CPU puts itself to sleep while all the onchip peripherals remain active. The mode is invoked by software. The content of the on-chip RAM and all the special functions registers remain unchanged during this mode. The idle mode can be terminated by any enabled interrupt or by a hardware reset. It should be noted that when idle is terminated by a hard ware reset, the device normally resumes program execution,from where it left off, up to two machine cycles before the internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this event, but access to the port pins is not inhibited. To eliminate the possibility of an unexpected write to a port pin when Idle is terminated by reset, the instruction following the one that invokes Idle should not be one that writes to a port pin or to external memory.Power-down ModeIn the power-down mode, the oscillator is stopped, and the instruction that invokes power-down is the last instruction executed. The on-chip RAM and Special Function Registers retain their values until the power-down mode is terminated. The only exit from power-down is a hardware reset. Reset redefines the SFRs but does not change the on-chip RAM. The reset should not be activated before VCC is restored to its normal operating level and must be held active long enough to allow the oscillator to restart and stabilize.The AT89C51 code memory array is programmed byte-bybyte in either programming mode. To program any nonblank byte in the on-chip Flash Memory, the entire memory must be erased using the Chip Erase Mode.2 Programming AlgorithmBefore programming the AT89C51, the address, data and control signals should be set up according to the Flash programming mode table and Figure 3 and Figure 4. To program the AT89C51, take the following steps.1. Input the desired memory location on the address lines.2. Input the appropriate data byte on the data lines. 3. Activate the correct combination of control signals. 4. Raise EA/VPP to 12V for the high-voltage programming mode.5. Pulse ALE/PROG once to program a byte in the Flash array or the lock bits. The byte-write cycle is self-timed and typically takes no more than 1.5 ms. Repeat steps 1 through 5, changing the address and data for the entire array or until the end of the object file is reached. Data Polling: The AT89C51 features Data Polling to indicate the end of a write cycle. During a write cycle, an attempted read of the last byte written will result in the complement of the written datum on PO.7. Once the write cycle has been completed, true data are valid on all outputs, and the next cycle may begin. Data Polling may begin any time after a write cycle has been initiated.2.1Ready/Busy:The progress of byte programming can also be monitored by the RDY/BSY output signal. P3.4 is pulled low after ALE goes high during programming to indicate BUSY. P3.4 is pulled high again when programming is done to indicate READY.Program Verify:If lock bits LB1 and LB2 have not been programmed, the programmed code data can be read back via the address and data lines for verification. The lock bits cannot be verified directly. Verification of the lock bits is achieved by observing that their features are enabled.Figure 2-1-1 Programming the Flash Figure 2-2-2 Verifying the Flash2.2 Chip Erase:The entire Flash array is erased electrically by using the propercombination of control signals and by holding ALE/PROG low for 10 ms. The code array is written with all “1”s. The chip erase operation must be executed before the code memory can be re-programmed.2.3 Reading the Signature Bytes:The signature bytes are read by the same procedure as a normal verification of locations 030H, 031H, and 032H, except that P3.6 and P3.7 must be pulled to a logic low. The values returned areas follows.(030H) = 1EH indicates manufactured by Atmel(031H) = 51H indicates 89C51(032H) = FFH indicates 12V programming(032H) = 05H indicates 5V programming2.4 Programming InterfaceEvery code byte in the Flash array can be written and the entire array can be erased by using the appropriate combination of control signals. The write operation cycle is selftimed and once initiated, will automatically time itself to completion. A microcomputer interface converts information between two forms. Outside the microcomputer the information handled by an electronic system exists as a physical signal, but within the program, it is represented numerically. The function of any interface can be broken down into a number of operations which modify the data in some way, so that the process of conversion between the external and internal forms is carried out in a number of steps. An analog-to-digital converter(ADC) is used to convert a continuously variable signal to a corresponding digital form which can take any one of a fixed number of possible binary values. If the output of the transducer does not vary continuously, no ADC is necessary. In this case the signal conditioning section must convert the incoming signal to a form which can be connected directly to the next part of the interface, the input/output section of the microcomputer itself. Output interfaces take a similar form, the obvious difference being that here the flow of information is in the opposite direction; it is passed from the program to the outside world. In this case the program may call an output subroutine which supervises the operation of the interface and performsthe scaling numbers which may be needed for digital-to-analog converter(DAC). This subroutine passes information in turn to an output device which produces a corresponding electrical signal, which could be converted into analog form using a DAC. Finally the signal is conditioned(usually amplified) to a form suitable for operating an actuator.The signals used within microcomputer circuits are almost always too small to be connected directly to the outside world” and some kind of interface must be used to translate them to a more appropriate form. The design of section of interface circuits is one of the most important tasks facing the engineer wishing to apply microcomputers. We have seen that in microcomputers information is represented as discrete patterns of bits; this digital form is most useful when the microcomputer is to be connected to equipment which can only be switched on or off, where each bit might represent the state of a switch or actuator. To solve real-world problems, a microcontroller must have more than just a CPU, a program, and a data memory. In addition, it must contain hardware allowing the CPU to access information from the outside world. Once the CPU gathers information and processes the data, it must also be able to effect change on some portion of the outside world. These hardware devices, called peripherals, are the CPU’s window to the outside.The most basic form of peripheral available on microcontrollers is the general purpose I70 port. Each of the I/O pins can be used as either an input or an output. The function of each pin is determined by setting or clearing corresponding bits in a corresponding data direction register during the initialization stage of a program. Each output pin may be driven to either a logic one or a logic zero by using CPU instructions to pin may be viewed (or read.) by the CPU using program instructions. Some type of serial unit is included on microcontrollers to allow the CPU to communicate bit-serially with external devices. Using a bit serial format instead of bit-parallel format requires fewer I/O pins to perform the communication function, which makes it less expensive, but slower. Serial transmissions are performed either synchronously or asynchronously.翻译AT89C51的概况1 AT89C51应用单片机广泛应用于商业：诸如调制解调器，电动机控制系统，空调控制系统，汽车发动机和其他一些领域。