# SXMicrocontrollerMathMethod

## Multiply 8 x 8 bits

```        LIST    P = 16C54, n = 66
;
;*******************************************************************
;                   8x8 Software Multiplier
;               ( Fast Version : Straight Line Code )
;*******************************************************************
;
;   The 16 bit result is stored in 2 bytes
;
; Before calling the subroutine " mpy ", the multiplier should
; be loaded in location " mulplr ", and the multiplicand in
; " mulcnd " . The 16 bit result is stored in locations
; H_byte & L_byte.
;
;       Performance :
;                       Program Memory  :  35 locations
;                       # of cycles     :  37
;                       Scratch RAM     :   0 locations
;
;
;       Program:          MULT8x8F.ASM
;       Revision Date:
;                         1-13-97      Compatibility with MPASMWIN 1.40
;
;  This routine is optimized for speed efficiency ( straight line code )
;  For code efficiency, refer to "mult8x8S.asm" ( looped code )
;*******************************************************************
;
mulcnd	equ	09	; 8 bit multiplicand
mulplr	equ	10	; 8 bit multiplier
H_byte	equ	12	; High byte of the 16 bit result
L_byte	equ	13	; Low byte of the 16 bit result
;
;
include         "p16c5x.inc"

Same	equ	1

;
;****   Define a macro for adding & right shifting  **
;
mult    MACRO   bit             ; Begin macro
snb	mulplr.bit
rr	H_byte
rr	L_byte
ENDM                    ; End of macro
;
; *****************************         Begin Multiplier Routine
mpy_F	clr	H_byte
clr	L_byte
mov	W, mulcnd	; move the multiplicand to W reg.
clrb	C	; Clear the carry bit in the status Reg.
mult    0
mult    1
mult    2
mult    3
mult    4
mult    5
mult    6
mult    7
;
retw	#0
;
;********************************************************************
;               Test Program
;*********************************************************************
main	mov	W, #0FF
mov	mulplr, W	; multiplier (in mulplr)     = 0FF
mov	W, #0FF
mov	mulcnd, W	; multiplicand(in mulcnd )   = 0FF
;
call	mpy_F	; The result 0FF*0FF = FE01 is in locations
;                               ; H_byte & L_byte
;
self	jmp	self
;
org	01FF
jmp	main
;
END

```

 file: /Techref/scenix/lib/math/mul/8x8u_sx.htm, 2KB, , updated: 2004/6/10 14:40, local time: 2024/9/11 04:05, TOP NEW HELP FIND:  3.236.100.210:LOG IN

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