diff --git a/imul8xe.s b/imul8xe.s deleted file mode 100644 index 855e044..0000000 --- a/imul8xe.s +++ /dev/null @@ -1,175 +0,0 @@ -FR0 = $d4 ; float48 -PORTB = $d301 - - -EXTENDED_RAM = $4000 ; 16KiB bank on the XE - -; lookup table for top byte -> PORTB value for bank-switch -.align 256 -bankswitch: - .repeat 256, i - .byte ((i & $c0) >> 5) | $c1 - .endrepeat - -; 58-77 cycles -; clobbers x, y, dest to dest + 3 -.macro imul8xe dest, arg1, arg2 -.local done -.local output -.local ptr - - output = dest - ptr = dest + 2 ; scratch space assumed - - ; bottom 14 bits except the LSB are the per-bank table index - ; add $4000 for the bank pointer - lda arg1 ; 3 cyc - and #$fe ; 2 cyc - sta ptr ; 3 cyc - lda arg2 ; 3 cyc - and #$3f ; 2 cyc - clc ; 2 cyc - adc #$40 ; 2 cyc - sta ptr + 1 ; 3 cyc - - ; top 2 bits are the table bank selector - ldx arg2 ; 3 cyc - lda bank_switch,x ; 4 cyc - sta PORTB ; 4 cyc - - - ; copy the entry into output - ldy #0 ; 2 cyc - lda (ptr),y ; 5 cyc - sta output ; 3 cyc - iny ; 2 cyc - lda (ptr),y ; 5 cyc - sta output+1 ; 3 cyc - - ; note: we are not restoring memory to save 6 cycles! - ; this means those 16kb have to be switched back to base RAM - ; if we need to use them anywhere else - ;;; restore memory - ;;lda #$81 ; 2 cyc - disabled - ;;sta PORTB ; 4 cyc - disabled - - ; check that 1 bit we skipped to fit into space - lda arg1 ; 3 cyc - and #1 ; 2 cyc - beq done ; 2 cyc - - ; add the second param one last time for the skipped bit - clc ; 2 cyc - lda arg2 ; 3 cyc - adc output ; 3 cyc - sta output ; 3 cyc - lda #0 ; 2 cyc - adc output+1 ; 3 cyc - sta output+1 ; 3 cyc - -done: -.endmacro - -.macro bank_switch bank - lda #((bank << 1) | $c1) - sta PORTB -.endmacro - -proc imul8xe_init - - ; go through the input set, in four 16KB chunks - - arg1 = FR1 - arg2 = FR2 - result = FR0 - - lda #$00 - sta arg1 - sta arg2 - - ; $00 * $00 -> $3f * $ff - bank_switch 0 - jsr imul8xe_init_section - - ; $40 * $00 -> $7f * $ff - bank_switch 1 - jsr imul8xe_init_section - - ; $80 * $00 -> $bf * $ff - bank_switch 2 - jsr imul8xe_init_section - - ; $c0 * $00 -> $ff * $ff - bank_switch 3 - jsr imul8xe_init_section - - rts -endproc - -; Initialize a 16 KB chunk of the table -; input: multipliers in temp -; output: new multipliers in temp -; clobbers: temp, temp2 -proc imul8xe_init_section - arg1 = FR1 - arg2 = FR2 - result = FR0 - ptr = temp2 - - lda #$00 - sta ptr - lda #$40 - sta ptr + 1 - - ldx #0 - ldy #0 - - ; outer loop: $00 -> $3f -outer_loop: - - ; reset result to 0 - lda #0 - sta result - sta result + 1 - - ; inner loop: $00 -> $ff -inner_loop: - - ; copy result to data set - lda result - sta (ptr),y - lda result + 1 - sta (ptr),y - - ; result += 2 * arg2 - clc - lda arg2 - adc result - sta result - lda #0 - adc result + 1 - sta result - lda arg2 - adc result - sta result - lda #0 - adc result + 1 - sta result - - ; inner loop check - inc arg1 - inc arg1 - inc ptr - inc ptr - bne inner_loop - - ; outer loop check - inc arg2 - inc ptr + 1 - lda ptr + 1 - cmp #$40 - bne outer_loop - - rts - -endproc