2.1.4多字节有符号数加法.txt

这是《MCS-51单片机应用开发实用子程序》配套源代码,对初学者很有用的

MADD1:	
MOV	A,R3						
ORL		A,R4
MADD6:	
CLR		OV
MOV	A,R6						
ORL		A,R7
MADD5:	
CLR		A						
MOV	R3,A
MOV	R4,A
MOV	R2,#41H
MOV	A,R7
MOV	B,R4
MOV	A,B
XCH		A,R7						
MOV	B,R3
ADD		A,R7						
MOV	R7,A
CLR		A
ADDC	A,B
XCH		A,R4
MOV	B,R6
ADD		A,R7
MOV	R7,A
MOV	A,B
ADDC	A,R4
MOV	R4,A
CLR		A
RLC		A						
XCH		A,R3
MOV	B,R6						
ADD		A,R4
MOV	R4,A
MOV	A,B
ADDC	A,R3
MOV	R3,A
JB		ACC.7,MADD2
MOV	A,R7
RLC	A
MOV	R7,A
RL1:
MOV	A,R4
RLC		A						
MOV	R4,A
MOV	A,R3
RLC		A
MOV	R3,A
DEC		R2
CJNE	R2,#0C0H,RL1E				
CLR		A						
MOV	R3,A
MOV	R4,A
MOV	R2,#0C1H
RET 
MADD2:	
MOV	A,R7
JNB		ACC.7,MADD3
INC		R4
MOV	A,R4
JNZ		MADD3
INC		R3
MOV	A,R3
JNZ		MADD3
MOV	R3,#80H
INC		R2
MADD3:	
MOV	A,R2
ADD		A,R5
RET