单片机第4章思考题与习题答案20101030
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第4章思考题与习题
7. 答:寻址方式目的操作数寻址方式源操作数寻址方式
ADD R1 ,B 寄存器寻址寄存器寻址
MOV A ,5AH 寄存器寻址直接寻址
MOV TH1 ,#02H 寄存器寻址立即数寻址
MOVC A,@A+DPTR 寄存器寻址变址寻址
XRL @R0 , A 寄存器间接寻址寄存器寻址
MOV C , 30H 位寻址位寻址
MOV DPTR , #4000H 寄存器寻址立即数寻址
ORL A , 20H 寄存器寻址直接寻址
MOVX A , @DPTR 寄存器寻址寄存器间接寻址
ANL C , 20H 位寻址位寻址
8. 在89C51片内RAM中 (30H)=38H,(38H)=40H,(40H)=48H,(48H)=90H。
分析下面指令,说明目的操作数和源操作数的寻址方式以及按顺序执行每条指令后的结果?
目的操作数源操作数
MOV A,40H ;寄存器寻址直接寻址(40H)→A A=48H
MOV R0,A ;寄存器寻址寄存器寻址(A)→R0 R0=48H
MOV P1,#0F0H ;寄存器寻址立即数寻址0F0→P1 P1=0F0H
MOV @R0,30H ;寄存器间接寻址直接寻址(30H)→(R0)(48H)=38H
MOV DPTR,#3848H ;寄存器寻址立即数寻址3848H→DPTR DPTR=3848H
MOV 40H,38H ;直接寻址直接寻址(38H)→40H (40H)=40H
MOV R0,30H ;寄存器寻址直接寻址(30H)→R0 R0=38H
MOV P0,R0 ;寄存器寻址寄存器寻址(R0 )→P0 P0=38H
MOV 18H,#30H ;直接寻址立即数寻址30H→18H (18H)=30H
MOV A,@R0 ;寄存器寻址寄存器间接寻址((R0)) →A A=40H
MOV P2,P1 ;寄存器寻址寄存器寻址(P1)→P2 P2=0F0H 最后结果:(R0)=38H,(A)=40H,(P0)=38H,(P1)=(P2)=0F0H,(DPTR)=3848H,(18H)=30H,(30H)=38H,(38H)=40H,(40H)=40H,(48H)=38H 注意:→左边是内容,右边是单元
9. 写出下列程序段的执行结果:
⑴.设:(A)=56H,(R5)=67H,
问执行下列指令后,A,R5及PSW中CY、AC、OV、P标志的内容如何?
执行指令:ADD A,R5
DA A
答:A=23H R5=67H
CY=1 AC=1 OV=0 P=1
⑵. 已知:A=83H R0=17H 片内RAM(17H)=34H
问执行下列指令后,累加器A、寄存器R0、关存储单元17H的内容如何?
执行指令:ANL A,#17H
ORL 17H , A
XRL A , @R0
CPL A
答:A=0CBH R0=17H (17H)=37H
⑶. 已知:(30H)=38H (38H)=40H (40H)=48H (48H)=90H
问执行下列指令后,各有关存储单元(即R0、R1、A、30H、38H、40H及48H单元)的内容如何?
执行指令:MOV A,40H
MOV R1,A
MOV @R1, 30H
MOV 40H , 38H
MOV R0,30H
MOV A , @R0
答:R0=38H R1=48H A=48H
(30H)=38H (38H)=40H (40H)=48H (48H)=38H
⑷.已知:内部RAM(30H)=5AH,(5AH)=40H,(40H)=00H,端口P1=7FH,
问执行下列指令后,有关存储单元(即R0,R1,A,B,P1,30H,40H及5AH单元)的内容如何?
执行指令:MOV R0,#30H
MOV A,@R0
MOV R1,A
MOV B,R1
MOV @R1,P1
MOV A,P1
MOV 40H,#20H
MOV 30H,40H
答:R0=30H R1=5AH A=7FH B=5FH P1=7FH
(30H)=20H (40H)=20H (5AH)=7FH
⑸. 已知:R0=20H,R1=25H,内部RAM的(20H)=80H,(21H)=90H,(22H)=A0H,
(25H)=A0H,(26H)=6FH,(27H)=76H
问执行下列指令后,各有关存储单元(即R0、R1、A、PSW、20H21H、22H、25H、26H、27H 单元)的内容如何?
执行指令:CLR C
MOV R2,#3
LOOP:MOV A,@R0
ADDC A , @ R1
MOV @R0 , A
INC R0
INC R1
DJNZ R2 , LOOP
JNC NEXT
MOV @ R0 , #01H
SJMP $
NEXT:DEC R0
SJMP $
答:R0=23H R1=28H A=17H PSW=80H
(20H)=20H (21H)=00H (22H)=17H (25H)=0A0H (26H)=6FH (27H)=76H (23H)=01H