mul.s43

msp430-book

;******************************************************************************
;   MSP430FG439 Integer Integer multiplication using the Algorithm explained in Hamacher
;
;   Description: This code performs a 16-bit 16-bit integer-integer multplication 
;                 of numbers 
;                 
;
;   Note:        This code assumes 32.768kHz XTAL on LFXT1 on the MSP430FG439 
;
;                 MSP430FG439
;               -----------------
;              |              XIN|-  
;              |                 | 32.768kHz
;              |             XOUT|-
;              |                 |
;
;
;   K. Venkat
;   Texas Instruments Inc.
;   July 2006
;   Built with IAR Embedded Workbench Version: 3.41A
;*******************************************************************************/
            public mul_hamacher
            RSEG CODE
mul_hamacher:

#define x1 R9
#define z0 R13
#define z1 R15
#define x  R12
#define y  R14

            push.w    R9

	    clr.w     z0
	    mov.w     z0,z1
	    mov.w     z0,x1
	    tst.w     x
	    jge	      xbooth_2
	    mov.w     #-1,x1
	    jmp       xbooth_2
xbooth_6
	    add.w     x,z1
	    addc.w    x1,z0
xbooth_1
	    rla.w     x
	    rlc.w     x1
xbooth_2
	    rra.w     y
	    jc	      xbooth_5
	    jne	      xbooth_1
	    jmp	      xbooth_4
xbooth_5
	    sub.w     x,z1
	    subc.w    x1,z0
xbooth_3
	    rla.w     x
	    rlc.w     x1
	    rra.w     y
	    jnc	      xbooth_6
	    cmp.w     #0FFFFh,y
	    jne	      xbooth_3
xbooth_4
            mov.w     z1,R12
            pop.w     R9
            ret
            END