/*------------------------------------------------------------------------------
* Program : Subroutine for that multiplies two 8-bit signed integers using HW multiplier
* Input      : The input parameters are:
                R12 -- array starting address
                R13 -- the number of elements (assume it is =>1)
                R14 -- dispay (0 for P1&P2 and 1 for P3&P4)
* Output     : No output parameters
*------------------------------------------------------------------------------*/
#include "msp430.h"                       ; #define controlled include file
         PUBLIC swmult
        RSEG CODE
swmult:
         ; save the registers on the stack
         PUSH     R7                      ; temporal sum
         CLR      R7
snext:   ADD      @R12+, R7
         DEC      R13
         JNZ      snext
         BIT      #1, R14                 ; display on P1&P2
         JNZ      sp34                    ; it's P3&P4
         MOV.B    R7, P1OUT
         SWPB     R7
         MOV.B    R7, P2OUT
         JMP      send
sp34:    MOV.B    R7, P3OUT
         SWPB     R7
         MOV.B    R7, P4OUT
send:    POP      R7                      ; restore R7
         RET
         END

Total := 0
Repeat
     C   := Op2 Mod 2
     Op2 := Op2 Div 2
     If C = 1 Then Total := Total + Op1
     Op1 := Op1 * 2
Until Op2 = 0


use RRA, lsb goes into C