2.2.1双字节无符号数减法.txt

MCS－51单片机应用开发实用子程序.zip

MOV	A,R6
CPL		ACC.7						
MOV	R6,A
JC		DAB2
NSUB:
MOV    	A,R4
SUB    	A,R7
MOV    	R4,A
MOV    	A,R3
SUBB   	A,R6
MOV    	R3,A
MOV    	A,R3
JB     	ACC.7,DABE
DAB1:
MOV    	C,SR0
MOV    	ACC.7,C
MOV    	R3,A
CLR    	OV
RET
DABE:
SETB   	OV							
RET
DAB2:
LCALL 	 NSUB						
MOV 	 A,R3
JNB		ACC.7,DAB1
LCALL  	CMPT
CPL    	SR0
SJMP   	DAB1
RET