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doc update (Byte 59)
| author | heinrichsweikamp |
|---|---|
| date | Sun, 23 Jun 2019 13:29:17 +0200 |
| parents | ca4556fb60b9 |
| children | c40025d8e750 |
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;============================================================================= ; ; File math.asm REFACTORED VERSION V2.99d ; ; Math subroutines ; ; Copyright (c) 2011, JD Gascuel, HeinrichsWeikamp, all right reserved. ;============================================================================= ; HISTORY ; 2011-08-03 : [mH] moving from OSTC code #include "hwos.inc" ; mandatory header math CODE ;============================================================================= global convert_time ; converts hi:lo in minutes to hours (up:hi) and minutes (lo) ; also usable for conversion of seconds to minutes and seconds ; trashes xA, xB, xC convert_time: movff lo,xA+0 ; copy hi:lo to xA movff hi,xA+1 ; movlw d'60' ; set divisor to 60 movwf xB+0 ; write 60 to xB clrf xB+1 ; rcall div16x16 ; xC = xA / xB with xA as remainder movff xC+1,up ; result is hours / minutes, copy to up (high byte) movff xC+0,hi ; result is hours / minutes, copy to hi (low byte) movff xA+0,lo ; remainder is minutes / seconds, copy to lo return global div16 ; divA:2 = divA:2 / 2^WREG ; trashes WREG div16: bcf STATUS,C ; clear carry rrcf divA+1 ; rotate right high byte, carry into MSB, LSB into carry rrcf divA+0 ; rotate right low byte, carry into MSB, LSB into carry decfsz WREG ; decrement counter, done? bra div16 ; NO - loop return ; YES - done global mult16 ; xA:2 = xA:2 * 2^WREG ; trashes WREG mult16: bcf STATUS,C ; clear carry rlcf divA+0,F ; rotate left low byte, carry into LSB, MSB into carry rlcf divA+1,F ; rotate left high byte, carry into LSB, MSB into carry decfsz WREG ; decrement counter, done? bra mult16 ; NO - loop return ; YES - done global sub16 ; sub_c:2 = sub_a:2 - sub_b:2 with SIGNED values ; sets neg_flag if result is < 0 ; trashes WREG sub16: bcf neg_flag ; clear flag which will indicate if result is negative movf sub_b+0,W ; get value to be subtracted, low byte subwf sub_a+0,W ; execute subtraction on low byte movwf sub_c+0 ; copy result to output variable, low byte movf sub_b+1,W ; get value to be subtracted, high byte subwfb sub_a+1,W ; execute subtraction on high byte, considering borrow flag movwf sub_c+1 ; copy result to output variable, high byte btfss STATUS,N ; result negative ? return ; NO - result positive, done bsf neg_flag ; YES - set flag comf sub_c+1 ; - do a 16 bit sign change negf sub_c+0 ; btfsc STATUS,C ; - carry to be propagated ? incf sub_c+1,F ; YES - do it return ; - done global subU16 ; sub_c:2 = sub_a:2 - sub_b:2 with UNSIGNED values ; sets neg_flag if result is < 0 ; trashes WREG subU16: bcf neg_flag ; clear flag which will indicate if result is negative movf sub_b+0,W ; get Value to be subtracted, low byte subwf sub_a+0,W ; execute subtraction on low byte movwf sub_c+0 ; copy result to output variable, low byte movf sub_b+1,W ; get value to be subtracted, high byte subwfb sub_a+1,W ; execute subtraction on high byte, considering borrow flag movwf sub_c+1 ; copy result to output variable, high byte btfsc STATUS,C ; borrow to propagate (B == /CARRY) ? return ; NO - result positive, done bsf neg_flag ; YES - set flag comf sub_c+1 ; - do a 16 bit sign change negf sub_c+0 ; btfsc STATUS,C ; - carry to be propagated ? incf sub_c+1,F ; YES - do it return ; - done global mult16x16 ; xC:4 = xA:2 * xB:2 with UNSIGNED values ; trashes PRODL, PRODH, WREG mult16x16: clrf xC+2 ; clear the high-order bits clrf xC+3 ; movf xA+0,W ; do the "L" multiplication mulwf xB+0 movff PRODL,xC+0 ; copy result to xC movff PRODH,xC+1 ; movf xA+0,W ; do the "I" multiplication mulwf xB+1 movf PRODL,W ; get the product's low byte... addwf xC+1,F ; ... and add it to xC+1 movf PRODH,W ; get the product's high byte... addwfc xC+2,F ; ... and add it to xC+2 obeying carry bit from xC+1 ; movf xA+1,W ; do the "O" multiplication mulwf xB+0 movf PRODL,W ; get the product's low byte... addwf xC+1,F ; ... and add it to xC+1 movf PRODH,W ; get the product's high byte... addwfc xC+2,F ; ... and add it to xC+2 obeying carry bit from xC+1 clrf WREG ; clear WREG... addwfc xC+3,F ; ... add add it to xC+3 obeying carry bit from xC+2 (can only happen in "O" multiplication) ; movf xA+1,W ; do the "F" multiplication mulwf xB+1 movf PRODL,W ; get the product's low byte... addwf xC+2,F ; ... and add it to xC+2 movf PRODH,W ; get the product's high byte... addwfc xC+3,F ; ... and add it to xC+3 obeying carry bit from xC+2 return global div16x16 ; xC:2 = xA:2 / xB:2 with xA as remainder ; trashes WREG div16x16: movlw .16 ; process 16 bits ... movwf math_loop ; ... initialize loop counter movff xA+0,xC+0 ; copy xA to xC movff xA+1,xC+1 ; ... clrf xA+0 ; clear xA, will now be used to hold the remainder clrf xA+1 ; ... div16x16_1: bcf STATUS,C ; clear carry flag to shift in a zero bit rlcf xC+0,F ; shift left xC rlcf xC+1,F ; ... shifting MSB out of xC... rlcf xA+0,F ; ... and into LSB of xA rlcf xA+1,F ; ... btfsc STATUS,C ; did the remainder overflow (carry set)? bra div16x16_2 ; YES - directly generate a result bit = 1 movf xB+0,W ; NO - compute remainder - divisor = xA - xB, trash result to WREG subwf xA+0,W ; - ... movf xB+1,W ; - ... subwfb xA+1,W ; - ... btfss STATUS,C ; - remainder < divisor (-> borrow flag set, equals carry flag cleared) ? bra div16x16_3 ; YES - result bit = 0, keep LSB of xC+0 being 0 div16x16_2: bsf xC+0,0 ; NO - result bit = 1, set LSB of xC+0 to 1 movf xB+0,W ; - subtract divisor from remainder "for real": xA = xA - xB subwf xA+0,F ; - ... movf xB+1,W ; - ... subwfb xA+1,F ; - ... div16x16_3: decfsz math_loop,F ; decrement loop counter, all bits done? bra div16x16_1 ; NO - loop return ; YES - done global div32x16 ; xC:4 = xC:4 / xB:2 with xA as remainder ; trashes WREG div32x16: movlw .32 ; process 32 bits ... movwf math_loop ; ... initialize loop counter clrf xA+0 ; clear xA, will be used to hold the remainder clrf xA+1 ; ... div32x16_1: bcf STATUS,C ; clear carry flag to shift in a zero bit rlcf xC+0,F ; shift left xC rlcf xC+1,F ; ... rlcf xC+2,F ; ... rlcf xC+3,F ; ... shifting MSB out of xC... rlcf xA+0,F ; ... and into LSB of xA rlcf xA+1,F ; ... btfsc STATUS,C ; did the remainder overflow (carry set)? bra div32x16_2 ; YES - directly generate a result bit = 1 movf xB+0,W ; NO - compute remainder - divisor = xA - xB, trash result to WREG subwf xA+0,W ; - ... movf xB+1,W ; - ... subwfb xA+1,W ; - ... btfss STATUS,C ; - remainder < divisor (-> borrow flag set, equals carry flag cleared) ? bra div32x16_3 ; YES - result bit = 0, keep LSB of xC+0 being 0 div32x16_2: bsf xC+0,0 ; NO - result bit = 1, set LSB of xC+0 to 1 movf xB+0,W ; - subtract divisor from remainder "for real": xA = xA - xB subwf xA+0,F ; - ... movf xB+1,W ; - ... subwfb xA+1,F ; - ... div32x16_3: decfsz math_loop,F ; decrement loop counter, all bits done? bra div32x16_1 ; NO - loop return ; YES - done ;============================================================================= ; ISR math functions global isr_shift_C31 ; 24 bit shift, repeated WREG times, dedicated to a specific usage: ; Because less than 8 bits are shifted and only C[2:1] is needed, ; we don't care what bit is inserted. isr_shift_C31: rrcf isr_xC+3,F ; shift three bytes rrcf isr_xC+2,F rrcf isr_xC+1,F decfsz WREG ; decrement loop counter, done? bra isr_shift_C31 ; NO - loop return ; YES - done global isr_unsigned_mult16x16 ; isr_xC = isr_xA * _isr_xB with UNSIGNED values ; trashes PRODL, PRODH, WREG isr_unsigned_mult16x16: movf isr_xA+0,W ; multiply a[0] * b[0] mulwf isr_xB+0 movff PRODL,isr_xC+0 ; store product to c[1]:c[0] movff PRODH,isr_xC+1 ; movf isr_xA+1,W ; multiply a[1] * b[1] mulwf isr_xB+1 movff PRODL, isr_xC+2 ; store product to c[3]:c[2] movff PRODH, isr_xC+3 ; movf isr_xA+0,W ; multiply a[0] * b[1] mulwf isr_xB+1 movf PRODL,W ; add cross product to c[3]:c[2]:c[1] addwf isr_xC+1,F movf PRODH,W addwfc isr_xC+2,F ; propagate carry clrf WREG addwfc isr_xC+3,F ; propagate carry ; movf isr_xA+1,W ; multiply a[1] * b[0] mulwf isr_xB+0 movf PRODL,W ; add cross product addwf isr_xC+1,F movf PRODH,W addwfc isr_xC+2,F ; propagate carry clrf WREG addwfc isr_xC+3,F ; propagate carry return global isr_signed_mult16x16 ; isr_xC = isr_xA * _isr_xB with SIGNED values ; trashes PRODL, PRODH, WREG isr_signed_mult16x16: rcall isr_unsigned_mult16x16 ; do an unsigned multiplication first ; ; manage sign extension of operand B btfss isr_xB+1,7 ; is B negative ? bra isr_signed_mult_checkA ; NO - continue checking operand A movf isr_xA+0,W ; Yes - add -65536 * A subwf isr_xC+2,F movf isr_xA+1,W subwfb isr_xC+3,F isr_signed_mult_checkA ; manage sign extension of operand B btfss isr_xA+1,7 ; is A negative ? return ; NO - done movf isr_xB+0,W ; Yes - add -65536 * B subwf isr_xC+2,F movf isr_xB+1,W subwfb isr_xC+3,F return END