1.3.3 双字节有符号数乘法.txt

数值算法,C51单片机的汇编程序

ORG		1000H
SDOMUL:
MOV	R0,#20H			
MOV	A,@R0			
ANL		A,#80H			
MOV	R3,A				
JZ		L1				
ACALL	L0				
L1:
INC		R0				
INC 		R0
MOV	A,@R0
ANL 	A,#80H
MOV	R2,A				
JZ		L2
ACALL	L0
L2:			
MOV	A,R3
XRL		A,R2				
MOV	08H,A			
MOV	R2,#4
MOV	R0,#20H
MOV	R1,#07H
L3:			
MOV	A,@R0
MOV	@R1,A
INC		R0				
DEC		R1				
DJNZ	R2,L3
MOV	R0,#30H			
LCALL	START			
MOV	A,80H			
JNZ		L4				
SJMP	L6
L4:	
CLR		C				
MOV	R0,#30H
MOV	R3,#3
MOV	A,@R0
CPL		A
ADD		A,#1				
MOV	@R0,A
L5:			
INC		R0				
MOV	A,@R0
CPL		A
ADDC	A,#0
MOV	@R0,A
DJNZ	R3,L5
L6:			
RET						
L0:			
CLR		C
INC		R0				
MOV	A,@R0
CPL		A
ADD		A,#1				
MOV	@R0,A
DEC		R0				
MOV	A,@R0
CPL		A
ADDC	A,#0
MOV	@R0,A
RET