单片机两位乘两位汇编的程序

mun:PUSH ACC
PUSH PSW
MOV R4,#0
MOV R5 ,#0
MOV R0,#16
CLR C
NEXT:ACALL RSHIFT
JNC NEXT1
MOV A,R5
ADD A,R3
MOV R5,A
MOV A,R4
ADDC A,R2
NEXT1:DJNZ R0,NEXT
ACALL RSHIFT
POP PSW
POP ACC
RET
RSHIFT:MOV A,R4
RRC A
MOV R4,A
MOV A,R5
RRC A
MOV R5,A
MOV A,R6
RRC A
MOV R6,A
MOV A,R7
RRC A
MOV R7,A
RET

16进制2位乘两位？