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PIC单片机论坛→论坛展示区（非讨论区）→『单片机类精华贴子展示区』→PIC单片机应用专题二：内、外EEPROM读写
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PIC单片机应用专题二：内、外EEPROM读写
以下内容只有回复后才可以浏览
EEPROM常用来保存应用系统的参数，有广泛的应用，下面给出内、外EEPROM读写例程：
1、16F877A内部EEPROM的读写：
LIST P=16f877A
#INCLUDE
;
;- RAM LOCATIONS------
;
; Reserve RAM location 0x70 for ICD
;
Data_EE_Addr equ 0X71
Data_EE_Data equ 0X72
;--------VECTORS------------
org 0x0
nop
goto START
;-------PROGRAM--------------
org 0X20
START
call INIT
;
;---- Test the WRITE EEPROM Routine ----
;
movlw 0x0
movwf Data_EE_Addr
movlw '0' ; Load a ASCII code "0" to W
movwf Data_EE_Data
EE_Write
call WRITE_EEPROM
incf Data_EE_Data,F ; 0x30+ N
incf Data_EE_Addr,F ; Point to next EEPROM Address
btfss Data_EE_Addr,5 ; Write 32 bytes ?
goto EE_Write
;
;---- Test the READ EEPROM Routine ----
;
movlw 0x20 ; Get back EEPROM data to RAM with start addr at 0x20 movwf FSR
;
movlw 0x0 ; Point to EEPROM start address at 0x00
movwf Data_EE_Addr
EE_Read
call READ_EEPROM ; Read EEPROM data with curent address to W registre movwf INDF ; move W --> RAM
;
incf FSR,F
incf Data_EE_Addr,F ; Point to next EEPROM Address
btfss Data_EE_Addr,6 ; Read 32 bytes ?
goto EE_Read
;
GOTO $
;
;------ INTERNAL EEPROM READ ------
;
READ_EEPROM
banksel EEADR
movf Data_EE_Addr,W ; Load EEPROM Address into Pointer
movwf EEADR
;
; bcf INTCON,GIE
banksel EECON1
bcf EECON1,EEPGD
bsf EECON1,RD
;
banksel EEDATA
movf EEDATA,W
; bsf INTCON,GIE
;
banksel PORTA
return
;
;----INTERNAL EEPROM WRITE-----
;
WRITE_EEPROM
banksel EEADR
movf Data_EE_Addr,W ; Load EEPROM Address & Data into Register movwf EEADR
movf Data_EE_Data,W
movwf EEDATA
;
banksel EECON1
bcf EECON1,EEPGD ; Selected Data EEPROM for Writing
bsf EECON1,WREN ; Enable write function
; bcf INTCON,GIE ; Disable Interrupt
movlw 0x55 ; Write Sequence control
movwf EECON2
movlw 0xAA
movwf EECON2
bsf EECON1,WR ; Start EEPROM write operation
;
; bsf INTCON,GIE ; Enable Interrupt (If used interrupt )
bcf EECON1,WREN ; Disable write EEPROM
;
btfsc EECON1,WR ; Waiting for writing completed (4mS)
goto $-1 ; During write period, must hold both EEADR & EEDATA until c omplete
;
banksel PORTA
return
;
;---------INITIAL----------------
INIT
BCF PIR2,EEIF
banksel PIE2
BCF PIE2,EEIE
RETURN
;--------------------------------
END
2、外部EEPROM的读写，所用EEPROM为AT93C46，MCU为16F877A，AT93C46的指令表为：
;*************************************************************
;; received bytes from EEPROM memory locations 10h to 13h
; will be stored in RAM registers 20h to 23h.
;eePROM 93C46读写演示程序。
;将0x5A写到93c46的10h～13h，再将其读到RAM的20h～23h
;硬件设置：SW1的1,2,3断开
;*************************************************************
;
;**********************************************************
LIST P=16F877A
INCLUDE "P16F877.INC"
; Ram Register Definitions
;**************************************************** ;
DISP1 EQU 20H
DISP2 EQU DISP1+1
DISP3 EQU DISP2+1
DISP4 EQU DISP3+1 ;以上为四位显示数据存放位
count EQU DISP4+1 ;动态显示位
T1 EQU count+1 ;延时数据存放位
ctrl EQU T1+1 ;动态显示控制位
outdb EQU ctrl+1
indb EQU outdb+1
i EQU indb+1
rxdata equ i+1
txdata equ rxdata+1
addr equ txdata+1
loops equ addr+1
loops2 equ loops+1
hibyte equ loops2+1
lobyte equ hibyte+1
datbyt equ lobyte+1
CKPMN equ datbyt+1
;**************************************************** ;
; Other Definitions
;
;**************************************************** ;
;
;**************************************************** ; Bit Definitions
;**************************************************** ;
cs equ 7
sdi equ 4
org 0x000 ; Reset Vector
NOP
goto Start
;
;*********************************************************** ;
; This is the transmit/receive routine. The received bytes ; are don't cares until reading back from the array.
;
;*********************************************************** output movwf outdb
clrf rxdata
movlw 0x09
movwf i
again decfsz i,1
goto dbtran
return
dbtran bcf PORTC,3
ckpn movlw 0x01
andwf outdb,0
btfss W,0
goto daout
bsf PORTC,5
datan bsf PORTC,3
movlw 0x02
movwf T1
call delay
ckpt rrf outdb,1
btfss PORTC,4
goto datas
bsf STATUS,0
datat rrf rxdata,1
goto again
daout bcf PORTC,5
goto datan
datas bcf STATUS,0
goto datat
;************************************************************ delay decfsz T1,1
goto delay
;************************************************************
;*********************************************************** ;
; EWEN routine
;
;***********************************************************
EWEN
bcf STATUS, RP0 ; need to set bank 0
bsf PORTC, cs ; set chip select line high
movlw b'00000010' ; start bit is bit 3, 00 is
; op code for EWEN
call output ;
movlw b'01100000' ; 1 req for EWEN, 0000000 are don't cares ; which is the 8 lsb address bits
call output ;
bcf PORTC, cs ; bring chip select low to begin
; EEPROMs internal write cycle
retlw 0 ; return from subroutine
; remember CS must be low for at least 250 nsec
;************************************************************
;************************************************************ ;
; This routine outputs the two bytes required to send
; the start bit, op code bits, and address bits
;
;************************************************************
bcf STATUS, RP0 ; need to set bank 0
bsf PORTC, cs ; set chip select line high
movf hibyte, 0 ; put hibyte in w reg
call output ;
movf FSR, 0 ; put addr pointed to by FSR into
; w reg
call output ;
movf datbyt, 0 ; get ready to output data in datbyt
call output ;
bcf PORTC, cs ; bring chip select low to begin
; EEPROMs internal write cycle
incf FSR, 1 ; point to next location to
; write to
retlw 0
;**************************************************************
;************************************************************** ;
; This is the module that reads one byte of data
;
;**************************************************************
READ
bcf STATUS, RP0 ; need to set bank 0
bsf PORTC, cs ; set chip select line high
bsf SSPCON, CKP ; make sure CKP is 1 to output
; next intstruction and addr
movf hibyte, 0 ; move data from hibyte to w
call output ;
movf lobyte, 0 ; get ready to send next byte
; which is the 8 lsb address bits
call output ;
;******************************************************** ; This is where CKP bit is reset for receiving data.
;******************************************************** bcf SSPCON, CKP ; change clock polarity to 0
movlw 0x00 ; The byte xmitted here is a
; don't care
call output ;
bcf PORTC, cs ; bring chip select low to
; terminate read command
clrf INDF ; clr location pointed to by FSR
movf rxdata, 0 ; move received data to w reg
movwf INDF ; put received data in location
; pointed to by FSR
incf FSR, 1 ; point to next location to
; write to
incf lobyte, 1 ; next addr to read from
retlw 0 ;
;************************************************************** ;**************************************************************
;************************************************************** ;************************************************************** Start
bcf STATUS, RP0 ; need to set bank 0
clrf PORTC ; initialize port c
bsf STATUS, RP0 ; need to set bank 1
movlw 0x10 ; all bits are outputs except SDI
movwf TRISC ; for SPI input
movlw 0x00
movwf SSPSTAT
clrf PIE1 ; disables all peripheral ints
clrf INTCON ; disables all interrupts
bcf STATUS, RP0 ; need to set bank 0
clrf SSPCON ; clear SSP control register
movlw 0x31 ; SPI master, clk/16, ckp=1
movwf SSPCON ; SSPEN enabled
;*******************************************************
; Now, lets read back 10h through 13h (non-sequentially) and ; store it in ram locations 20h through 23h in the 16C74.
; With the Picmaster, I can read those memory locations
; and see that it was read in properly. This is how
; I can quickly verify that the read function is working
; properly.
;*******************************************************
movlw 0x20 ; where in RAM to begin storing
movwf FSR ; data read back from EEPROM
movlw 0x10 ; addr of where to begin reading
movwf lobyte ; EEPROM from
movlw b'00000011' ; start bit is bit 3, 10 is
movwf hibyte ; op code for read
rdnext call READ ;
btfss FSR, 2 ; have we 20h thru 23?
goto rdnext ; no, then read next location
;******************************************************** ; While program is in limbo routine, it is possible
; to halt the processor with Picmaster and look at
; the data contained 16C74 RAM locations 20h through 23h. ;******************************************************** limbo nop
goto limbo
;
;
end