Untitled

#include"xc.inc"
  GLOBAL _multi_signed
  
  PSECT mytext,local,class=CODE,reloc=2
  
_multi_signed:
    MOVWF 0x00
    BTFSS 0x00, 7
    GOTO Positive
    GOTO Negative

Positive:
    BTFSS 0x01, 3
    GOTO PMulP
    GOTO PMulN

    
Negative:
    BTFSS 0x01, 3
    GOTO NMulP
    GOTO NMulN
    
PMulN:
    COMF 0x01
    MOVF 0x00, W
    MOVWF 0x11
    RCALL Multiplication
    GOTO NegativeFinish

PMulP:
    DECF 0x01
    MOVF 0x00, W
    MOVWF 0x11
    RCALL Multiplication
    GOTO PositiveFinish

NMulN:
    COMF 0x00
    INCF 0x00
    COMF 0x01

    MOVF 0x00, W
    MOVWF 0x11
    RCALL Multiplication
    GOTO PositiveFinish
    
NMulP:
    COMF 0x00
    INCF 0x00
    DECF 0x01
    MOVF 0x00, W
    MOVWF 0x11
    RCALL Multiplication
    GOTO NegativeFinish

Multiplication:
    ADDWF 0x11
    BTFSC STATUS, 0
    INCF 0x10
    DECFSZ 0x01
    GOTO Multiplication
    RETURN
    

PositiveFinish:
    MOVFF 0x11, 0x01
    MOVFF 0x10, 0x02
    RETURN

NegativeFinish:
    MOVFF 0x11, 0x01
    COMF 0x01
    INCF 0x01
    MOVFF 0x10, 0x02
    COMF 0x02
    RETURN