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 add H_byte, W 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
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