2.3.2多字节无符号数乘法.txt

MCS51单片机相关设计用到的一些子程序。用ASM文件编写

FMUL:	
MOV	A,R3					
ORL		A,R4
JZ		MUL6
MOV	A,R6						
ORL		A,R7
JZ		MUL5
MOV	A,R7						
MOV	B,R4
MUL		AB
MOV	A,B
XCH		A,R7
MOV	B,R3
MUL		AB
ADD		A,R7
MOV	R7,A
CLR		A
ADDC	A,B
XCH		A,R4					
MOV	B,R6
MUL		AB						
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
MUL		AB
ADD		A,R4
MOV	R4,A
MOV	A,B
ADDC	A,R3
MOV	R3,A
JB		ACC.7,MUL2				
MOV	A,R7						
RLC		A
MOV	R7,A
LCALL	RL1
MUL2:	
MOV	A,R7
JNB		ACC.7,MUL3
INC		R4						
MOV	A,R4
JNZ		MUL3
INC		R3
MOV	A,R3
JNZ		MUL3
MOV	R3,#80H
INC		R2
MUL3:
MOV	A,R2						
ADD		A,R5
MD:	
MOV	R2,A						
JB		ACC.7,MUL4
JNB		ACC.6,MUL6
MOV	R2,#3FH					
SETB	OV
RET
MUL4:	
JB		ACC.6,MUL6
MUL5:	
CLR		A						
MOV	R3,A
MOV	R4,A
MOV	R2,#41H
MUL6:	
CLR		OV
RET