ch18_内部数据存储器的4字节相减.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:DATA_SUBTRACT
     ;FUNCTION:SUBTRACT 4 BYTES,RESULT IN DATA MEMORY
     ;(R0+3)(R0+2)(R0+1)(R0)=(R0+3)(R0+2)(R0+1)(R0)-(R1+3)(R1+2)(R1+1)(R1)
     ;
     DATA_SUBTRACT
           	MOV   	R2,#04H
           	CLR   	C
     $1    	MOV   	A,@R0
           	SUBB  	A,@R1
           	MOV   	@R0,A
           	INC   	R0
           	INC   	R1
           	DJNZ  	R2,$1
           	RET
     ;