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: EXTERNAL_DATA_COMPARE
				     ;FUNCTION: COMPARE 2 BLOCKS EXTERNAL DATA MEMORY(R2)TIMES
				     ;BLOCK 1 START AT DPTR
				     ;BLOCK 2 START AT R7,R6
				     ;
				     EXTERNAL_DATA_COMPARE
				     $1   	MOVX 	A,@DPTR
				           	MOV   	B,A       	;BLOCK 1 DATA IN B
				           	PUSH  	DPH  
				           	PUSH  	DPL
				           	MOV   	DPH,R7
				           	MOV   	DPL,R6
				           	MOVX  	A,@DPTR  	;BLOCK 2 DATA IN A
				           	INC   	DPTR
				           	MOV   	R7,DPH
				           	MOV   	R6,DPL   	;BLOCK 2 INDEX+1
				           	POP   	DPL
				           	POP   	DPH
				           	INC   	DPTR     	;BLOCK 1 INDEX+1
				           	CJNE  	A,B,$2   	;COMPARE 1 BYTE
				           	DJNZ  	R2,$1
				           	MOV   	A,#00H    	;NO ERROR
				           	SJMP  	$2+2
				     $2       MOV   	A,#01H    	;ERROR
				           	RET
				     ;