; Internal Math library routines - always included by the compiler ; Generic machine independent 6502 code. ; ; some more interesting routines can be found here: ; http://6502org.wikidot.com/software-math ; http://codebase64.org/doku.php?id=base:6502_6510_maths ; multiply_bytes .proc ; -- multiply 2 bytes A and Y, result as byte in A (signed or unsigned) sta P8ZP_SCRATCH_B1 ; num1 sty P8ZP_SCRATCH_REG ; num2 lda #0 beq _enterloop _doAdd clc adc P8ZP_SCRATCH_B1 _loop asl P8ZP_SCRATCH_B1 _enterloop lsr P8ZP_SCRATCH_REG bcs _doAdd bne _loop rts .pend multiply_bytes_into_word .proc ; -- multiply 2 bytes A and Y, result as word in A/Y (unsigned) sta P8ZP_SCRATCH_B1 sty P8ZP_SCRATCH_REG lda #0 ldx #8 lsr P8ZP_SCRATCH_B1 - bcc + clc adc P8ZP_SCRATCH_REG + ror a ror P8ZP_SCRATCH_B1 dex bne - tay lda P8ZP_SCRATCH_B1 rts .pend multiply_words .proc ; -- multiply two 16-bit words into a 32-bit result (signed and unsigned) ; input: A/Y = first 16-bit number, P8ZP_SCRATCH_W1 in ZP = second 16-bit number ; output: multiply_words.result 4-bytes/32-bits product, LSB order (low-to-high) low 16 bits also in AY. sta P8ZP_SCRATCH_W2 sty P8ZP_SCRATCH_W2+1 mult16 lda #0 sta result+2 ; clear upper bits of product sta result+3 ldx #16 ; for all 16 bits... - lsr P8ZP_SCRATCH_W1+1 ; divide multiplier by 2 ror P8ZP_SCRATCH_W1 bcc + lda result+2 ; get upper half of product and add multiplicand clc adc P8ZP_SCRATCH_W2 sta result+2 lda result+3 adc P8ZP_SCRATCH_W2+1 + ror a ; rotate partial product sta result+3 ror result+2 ror result+1 ror result dex bne - lda result ldy result+1 rts result .byte 0,0,0,0 .pend divmod_b_asm .proc ; signed byte division: make everything positive and fix sign afterwards sta P8ZP_SCRATCH_B1 tya eor P8ZP_SCRATCH_B1 php ; save sign lda P8ZP_SCRATCH_B1 bpl + eor #$ff sec adc #0 ; make it positive + pha tya bpl + eor #$ff sec adc #0 ; make it positive tay + pla jsr divmod_ub_asm sta _remainder plp bpl + tya eor #$ff sec adc #0 ; negate result tay + rts _remainder .byte 0 .pend divmod_ub_asm .proc ; -- divide A by Y, result quotient in Y, remainder in A (unsigned) ; division by zero will result in quotient = 255 and remainder = original number sty P8ZP_SCRATCH_REG sta P8ZP_SCRATCH_B1 lda #0 ldx #8 asl P8ZP_SCRATCH_B1 - rol a cmp P8ZP_SCRATCH_REG bcc + sbc P8ZP_SCRATCH_REG + rol P8ZP_SCRATCH_B1 dex bne - ldy P8ZP_SCRATCH_B1 rts .pend divmod_w_asm .proc ; signed word division: make everything positive and fix sign afterwards sta P8ZP_SCRATCH_W2 sty P8ZP_SCRATCH_W2+1 lda P8ZP_SCRATCH_W1+1 eor P8ZP_SCRATCH_W2+1 php ; save sign lda P8ZP_SCRATCH_W1+1 bpl + lda #0 sec sbc P8ZP_SCRATCH_W1 sta P8ZP_SCRATCH_W1 lda #0 sbc P8ZP_SCRATCH_W1+1 sta P8ZP_SCRATCH_W1+1 + lda P8ZP_SCRATCH_W2+1 bpl + lda #0 sec sbc P8ZP_SCRATCH_W2 sta P8ZP_SCRATCH_W2 lda #0 sbc P8ZP_SCRATCH_W2+1 sta P8ZP_SCRATCH_W2+1 + tay lda P8ZP_SCRATCH_W2 jsr divmod_uw_asm plp ; restore sign bpl + sta P8ZP_SCRATCH_W2 sty P8ZP_SCRATCH_W2+1 lda #0 sec sbc P8ZP_SCRATCH_W2 pha lda #0 sbc P8ZP_SCRATCH_W2+1 tay pla + rts .pend divmod_uw_asm .proc ; -- divide two unsigned words (16 bit each) into 16 bit results ; input: P8ZP_SCRATCH_W1 in ZP: 16 bit number, A/Y: 16 bit divisor ; output: P8ZP_SCRATCH_W2 in ZP: 16 bit remainder, A/Y: 16 bit division result ; division by zero will result in quotient = 65535 and remainder = divident dividend = P8ZP_SCRATCH_W1 remainder = P8ZP_SCRATCH_W2 result = dividend ;save memory by reusing divident to store the result sta _divisor sty _divisor+1 lda #0 ;preset remainder to 0 sta remainder sta remainder+1 ldx #16 ;repeat for each bit: ... - asl dividend ;dividend lb & hb*2, msb -> Carry rol dividend+1 rol remainder ;remainder lb & hb * 2 + msb from carry rol remainder+1 lda remainder sec sbc _divisor ;substract divisor to see if it fits in tay ;lb result -> Y, for we may need it later lda remainder+1 sbc _divisor+1 bcc + ;if carry=0 then divisor didn't fit in yet sta remainder+1 ;else save substraction result as new remainder, sty remainder inc result ;and INCrement result cause divisor fit in 1 times + dex bne - lda result ldy result+1 rts _divisor .word 0 .pend randword .proc ; -- 16 bit pseudo random number generator into AY ; default seed = $00c2 $1137 ; routine from https://codebase64.org/doku.php?id=base:x_abc_random_number_generator_8_16_bit inc x1 clc x1=*+1 lda #$00 ;x1 c1=*+1 eor #$c2 ;c1 a1=*+1 eor #$11 ;a1 sta a1 b1=*+1 adc #$37 ;b1 sta b1 lsr a eor a1 adc c1 sta c1 ldy b1 rts .pend randbyte = randword ; -- 8 bit pseudo random number generator into A (by just reusing randword) ; ----------- optimized multiplications (in-place A (byte) and ?? (word)) : --------- mul_byte_3 .proc ; A = A + A*2 sta P8ZP_SCRATCH_REG asl a clc adc P8ZP_SCRATCH_REG rts .pend mul_word_3 .proc ; AY = AY*2 + AY sta P8ZP_SCRATCH_W1 sty P8ZP_SCRATCH_W1+1 sta P8ZP_SCRATCH_W2 sty P8ZP_SCRATCH_W2+1 asl a rol P8ZP_SCRATCH_W1+1 clc adc P8ZP_SCRATCH_W2 sta P8ZP_SCRATCH_W1 lda P8ZP_SCRATCH_W1+1 adc P8ZP_SCRATCH_W2+1 tay lda P8ZP_SCRATCH_W1 rts .pend mul_byte_5 .proc ; A = A*4 + A sta P8ZP_SCRATCH_REG asl a asl a clc adc P8ZP_SCRATCH_REG rts .pend mul_word_5 .proc ; AY = AY*4 + AY sta P8ZP_SCRATCH_W1 sty P8ZP_SCRATCH_W1+1 sta P8ZP_SCRATCH_W2 sty P8ZP_SCRATCH_W2+1 asl a rol P8ZP_SCRATCH_W1+1 asl a rol P8ZP_SCRATCH_W1+1 clc adc P8ZP_SCRATCH_W2 sta P8ZP_SCRATCH_W1 lda P8ZP_SCRATCH_W1+1 adc P8ZP_SCRATCH_W2+1 tay lda P8ZP_SCRATCH_W1 rts .pend mul_byte_6 .proc ; A = (A*2 + A)*2 sta P8ZP_SCRATCH_REG asl a clc adc P8ZP_SCRATCH_REG asl a rts .pend mul_word_6 .proc ; AY = (AY*2 + AY)*2 sta P8ZP_SCRATCH_W1 sty P8ZP_SCRATCH_W1+1 sta P8ZP_SCRATCH_W2 sty P8ZP_SCRATCH_W2+1 asl a rol P8ZP_SCRATCH_W1+1 clc adc P8ZP_SCRATCH_W2 sta P8ZP_SCRATCH_W1 tay lda P8ZP_SCRATCH_W1+1 adc P8ZP_SCRATCH_W2+1 sta P8ZP_SCRATCH_W1+1 tya asl a rol P8ZP_SCRATCH_W1+1 ldy P8ZP_SCRATCH_W1+1 rts .pend mul_byte_7 .proc ; A = A*8 - A sta P8ZP_SCRATCH_REG asl a asl a asl a sec sbc P8ZP_SCRATCH_REG rts .pend mul_word_7 .proc ; AY = AY*8 - AY sta P8ZP_SCRATCH_W1 sty P8ZP_SCRATCH_W1+1 sta P8ZP_SCRATCH_W2 sty P8ZP_SCRATCH_W2+1 asl a rol P8ZP_SCRATCH_W1+1 asl a rol P8ZP_SCRATCH_W1+1 asl a rol P8ZP_SCRATCH_W1+1 sec sbc P8ZP_SCRATCH_W2 sta P8ZP_SCRATCH_W1 lda P8ZP_SCRATCH_W1+1 sbc P8ZP_SCRATCH_W2+1 tay lda P8ZP_SCRATCH_W1 rts .pend mul_byte_9 .proc ; A = A*8 + A sta P8ZP_SCRATCH_REG asl a asl a asl a clc adc P8ZP_SCRATCH_REG rts .pend mul_word_9 .proc ; AY = AY*8 + AY sta P8ZP_SCRATCH_W1 sty P8ZP_SCRATCH_W1+1 sta P8ZP_SCRATCH_W2 sty P8ZP_SCRATCH_W2+1 asl a rol P8ZP_SCRATCH_W1+1 asl a rol P8ZP_SCRATCH_W1+1 asl a rol P8ZP_SCRATCH_W1+1 clc adc P8ZP_SCRATCH_W2 sta P8ZP_SCRATCH_W1 lda P8ZP_SCRATCH_W1+1 adc P8ZP_SCRATCH_W2+1 tay lda P8ZP_SCRATCH_W1 rts rts .pend mul_byte_10 .proc ; A=(A*4 + A)*2 sta P8ZP_SCRATCH_REG asl a asl a clc adc P8ZP_SCRATCH_REG asl a rts .pend mul_word_10 .proc ; AY=(AY*4 + AY)*2 sta P8ZP_SCRATCH_W1 sty P8ZP_SCRATCH_W1+1 sta P8ZP_SCRATCH_W2 sty P8ZP_SCRATCH_W2+1 asl a rol P8ZP_SCRATCH_W1+1 asl a rol P8ZP_SCRATCH_W1+1 clc adc P8ZP_SCRATCH_W2 sta P8ZP_SCRATCH_W1 lda P8ZP_SCRATCH_W1+1 adc P8ZP_SCRATCH_W2+1 sta P8ZP_SCRATCH_W1+1 lda P8ZP_SCRATCH_W1 asl a rol P8ZP_SCRATCH_W1+1 ldy P8ZP_SCRATCH_W1+1 rts .pend mul_byte_11 .proc ; A=(A*2 + A)*4 - A sta P8ZP_SCRATCH_REG asl a clc adc P8ZP_SCRATCH_REG asl a asl a sec sbc P8ZP_SCRATCH_REG rts .pend ; mul_word_11 is skipped (too much code) mul_byte_12 .proc ; A=(A*2 + A)*4 sta P8ZP_SCRATCH_REG asl a clc adc P8ZP_SCRATCH_REG asl a asl a rts .pend mul_word_12 .proc ; AY=(AY*2 + AY)*4 sta P8ZP_SCRATCH_W1 sty P8ZP_SCRATCH_W1+1 sta P8ZP_SCRATCH_W2 sty P8ZP_SCRATCH_W2+1 asl a rol P8ZP_SCRATCH_W1+1 clc adc P8ZP_SCRATCH_W2 sta P8ZP_SCRATCH_W1 lda P8ZP_SCRATCH_W1+1 adc P8ZP_SCRATCH_W2+1 sta P8ZP_SCRATCH_W1+1 lda P8ZP_SCRATCH_W1 asl a rol P8ZP_SCRATCH_W1+1 asl a rol P8ZP_SCRATCH_W1+1 ldy P8ZP_SCRATCH_W1+1 rts .pend mul_byte_13 .proc ; A=(A*2 + A)*4 + A sta P8ZP_SCRATCH_REG asl a clc adc P8ZP_SCRATCH_REG asl a asl a clc adc P8ZP_SCRATCH_REG rts .pend ; mul_word_13 is skipped (too much code) mul_byte_14 .proc ; A=(A*8 - A)*2 sta P8ZP_SCRATCH_REG asl a asl a asl a sec sbc P8ZP_SCRATCH_REG asl a rts .pend ; mul_word_14 is skipped (too much code) mul_byte_15 .proc ; A=A*16 - A sta P8ZP_SCRATCH_REG asl a asl a asl a asl a sec sbc P8ZP_SCRATCH_REG rts .pend mul_word_15 .proc ; AY = AY * 16 - AY sta P8ZP_SCRATCH_W1 sty P8ZP_SCRATCH_W1+1 sta P8ZP_SCRATCH_W2 sty P8ZP_SCRATCH_W2+1 asl a rol P8ZP_SCRATCH_W1+1 asl a rol P8ZP_SCRATCH_W1+1 asl a rol P8ZP_SCRATCH_W1+1 asl a rol P8ZP_SCRATCH_W1+1 sec sbc P8ZP_SCRATCH_W2 sta P8ZP_SCRATCH_W1 lda P8ZP_SCRATCH_W1+1 sbc P8ZP_SCRATCH_W2+1 tay lda P8ZP_SCRATCH_W1 rts .pend mul_byte_20 .proc ; A=(A*4 + A)*4 sta P8ZP_SCRATCH_REG asl a asl a clc adc P8ZP_SCRATCH_REG asl a asl a rts .pend mul_word_20 .proc ; AY = AY * 10 * 2 jsr mul_word_10 sty P8ZP_SCRATCH_REG asl a rol P8ZP_SCRATCH_REG ldy P8ZP_SCRATCH_REG rts .pend mul_byte_25 .proc ; A=(A*2 + A)*8 + A sta P8ZP_SCRATCH_REG asl a clc adc P8ZP_SCRATCH_REG asl a asl a asl a clc adc P8ZP_SCRATCH_REG rts .pend mul_word_25 .proc ; AY = (AY*2 + AY) *8 + AY sta P8ZP_SCRATCH_W1 sty P8ZP_SCRATCH_W1+1 sta P8ZP_SCRATCH_W2 sty P8ZP_SCRATCH_W2+1 asl a rol P8ZP_SCRATCH_W1+1 clc adc P8ZP_SCRATCH_W2 sta P8ZP_SCRATCH_W1 lda P8ZP_SCRATCH_W1+1 adc P8ZP_SCRATCH_W2+1 sta P8ZP_SCRATCH_W1+1 lda P8ZP_SCRATCH_W1 asl a rol P8ZP_SCRATCH_W1+1 asl a rol P8ZP_SCRATCH_W1+1 asl a rol P8ZP_SCRATCH_W1+1 clc adc P8ZP_SCRATCH_W2 sta P8ZP_SCRATCH_W1 lda P8ZP_SCRATCH_W1+1 adc P8ZP_SCRATCH_W2+1 tay lda P8ZP_SCRATCH_W1 rts .pend mul_byte_40 .proc and #7 tay lda _forties,y rts _forties .byte 0*40, 1*40, 2*40, 3*40, 4*40, 5*40, 6*40, 7*40 & 255 .pend mul_word_40 .proc ; AY = (AY*4 + AY)*8 sta P8ZP_SCRATCH_W1 sty P8ZP_SCRATCH_W1+1 sta P8ZP_SCRATCH_W2 sty P8ZP_SCRATCH_W2+1 asl a rol P8ZP_SCRATCH_W1+1 asl a rol P8ZP_SCRATCH_W1+1 clc adc P8ZP_SCRATCH_W2 sta P8ZP_SCRATCH_W1 lda P8ZP_SCRATCH_W1+1 adc P8ZP_SCRATCH_W2+1 asl P8ZP_SCRATCH_W1 rol a asl P8ZP_SCRATCH_W1 rol a asl P8ZP_SCRATCH_W1 rol a tay lda P8ZP_SCRATCH_W1 rts .pend mul_byte_50 .proc and #7 tay lda _fifties, y rts _fifties .byte 0*50, 1*50, 2*50, 3*50, 4*50, 5*50, 6*50 & 255, 7*50 & 255 .pend mul_word_50 .proc ; AY = AY * 25 * 2 jsr mul_word_25 sty P8ZP_SCRATCH_REG asl a rol P8ZP_SCRATCH_REG ldy P8ZP_SCRATCH_REG rts .pend mul_byte_80 .proc and #3 tay lda _eighties, y rts _eighties .byte 0*80, 1*80, 2*80, 3*80 .pend mul_word_80 .proc ; AY = AY * 40 * 2 jsr mul_word_40 sty P8ZP_SCRATCH_REG asl a rol P8ZP_SCRATCH_REG ldy P8ZP_SCRATCH_REG rts .pend mul_byte_100 .proc and #3 tay lda _hundreds, y rts _hundreds .byte 0*100, 1*100, 2*100, 3*100 & 255 .pend mul_word_100 .proc ; AY = AY * 25 * 4 jsr mul_word_25 sty P8ZP_SCRATCH_REG asl a rol P8ZP_SCRATCH_REG asl a rol P8ZP_SCRATCH_REG ldy P8ZP_SCRATCH_REG rts .pend mul_word_320 .proc ; AY = A * 256 + A * 64 (msb in Y doesn't matter) sta P8ZP_SCRATCH_B1 ldy #0 sty P8ZP_SCRATCH_REG asl a rol P8ZP_SCRATCH_REG asl a rol P8ZP_SCRATCH_REG asl a rol P8ZP_SCRATCH_REG asl a rol P8ZP_SCRATCH_REG asl a rol P8ZP_SCRATCH_REG asl a rol P8ZP_SCRATCH_REG pha clc lda P8ZP_SCRATCH_B1 adc P8ZP_SCRATCH_REG tay pla rts .pend mul_word_640 .proc ; AY = (A * 2 * 320) (msb in Y doesn't matter) asl a jmp mul_word_320 .pend ; ----------- end optimized multiplications ----------- ; support for bit shifting that is too large to be unrolled: lsr_byte_A .proc ; -- lsr signed byte in A times the value in Y (>1) cmp #0 bmi _negative - lsr a dey bne - rts _negative sec ror a dey bne _negative rts .pend lsr_word_AY .proc ; -- lsr signed word in AY times the value in X (>1) sta P8ZP_SCRATCH_B1 tya bmi _negative - lsr a ror P8ZP_SCRATCH_B1 dex bne - tay lda P8ZP_SCRATCH_B1 rts _negative sec ror a ror P8ZP_SCRATCH_B1 dex bne _negative tay lda P8ZP_SCRATCH_B1 rts .pend square .proc ; -- calculate square root of signed word in AY, result in AY ; routine by Lee Davsion, source: http://6502.org/source/integers/square.htm ; using this routine is about twice as fast as doing a regular multiplication. ; ; Calculates the 16 bit unsigned integer square of the signed 16 bit integer in ; Numberl/Numberh. The result is always in the range 0 to 65025 and is held in ; Squarel/Squareh ; ; The maximum input range is only +/-255 and no checking is done to ensure that ; this is so. ; ; This routine is useful if you are trying to draw circles as for any circle ; ; x^2+y^2=r^2 where x and y are the co-ordinates of any point on the circle and ; r is the circle radius numberl = P8ZP_SCRATCH_W1 ; number to square low byte numberh = P8ZP_SCRATCH_W1+1 ; number to square high byte squarel = P8ZP_SCRATCH_W2 ; square low byte squareh = P8ZP_SCRATCH_W2+1 ; square high byte tempsq = P8ZP_SCRATCH_B1 ; temp byte for intermediate result sta numberl sty numberh lda #$00 ; clear a sta squarel ; clear square low byte ; (no need to clear the high byte, it gets shifted out) lda numberl ; get number low byte ldx numberh ; get number high byte bpl _nonneg ; if +ve don't negate it ; else do a two's complement eor #$ff ; invert sec ; +1 adc #$00 ; and add it _nonneg: sta tempsq ; save abs(number) ldx #$08 ; set bit count _nextr2bit: asl squarel ; low byte *2 rol squareh ; high byte *2+carry from low asl a ; shift number byte bcc _nosqadd ; don't do add if c = 0 tay ; save a clc ; clear carry for add lda tempsq ; get number adc squarel ; add number^2 low byte sta squarel ; save number^2 low byte lda #$00 ; clear a adc squareh ; add number^2 high byte sta squareh ; save number^2 high byte tya ; get a back _nosqadd: dex ; decrement bit count bne _nextr2bit ; go do next bit lda squarel ldy squareh rts .pend