ch18_检查一段外部数据存储器（2kb）的读写功能.asm

51单片机基础篇 对于有一定基础的人看看 包含书中所以的源代码

     ;FUNCTION NAME: CHECK_RAM_RW
     :FUNCTION: CHECK RAM READ/WRITE FUNCTION (2048 BYTES)
     ;RAM ADDRESS IN DPTR
     ;
     CHECK_RAM_RW
           	MOV   	R0,#08H
     $1 	MOV  	R1,#00H
     $2 	MOVX 	A,@DPTR   		;READ
           	XRL	A,#FFH
           	MOV   	B,A
           	MOVX 	@DPTR,A			;WRITE
           	MOVX 	A,@DPTR			;READ AGAIN
           	CJNE 	A,B,$3 			;READ/WRITE ERROR
           	XRL   	A,#FFH
           	MOVX 	@DPTR,A  		;WRITE AGAIN
           	INC   	DPTR
           	DJNZ 	R1,$2
           	DJNZ 	R0,$1
           	MOV   	A,#00H 			;IF NO ERROR THEN RETURN 0
           	SJMP 	$3+2
     $3 	MOV   	A,#01H
           	RET
     ;