145 lines
1.7 KiB
ArmAsm
145 lines
1.7 KiB
ArmAsm
;; Works similar to $BDCD in original C64 BASIC
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;; XXX Should eventually get replaced by a more flexible and optimal routine.
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;; Temp result gets written to $0100-$0104
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print_integer:
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pha
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txa
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pha
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;; Clear temporary output
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lda #$00
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ldy #5
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* sta $0100,y
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dey
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bpl -
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pla
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ldy #23 ; 8 x 3 - 1 = offset of last digit of 128
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lo_loop:
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cmp #$7f
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bcc bit_clear
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;; Bit set, so add the digits
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pha
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ldx #2
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clc
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lo_add_loop:
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lda $0102,x
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adc number_table_lo,y
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sta $0102,x
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dey
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dex
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bpl lo_add_loop
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pla
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jmp next_lo_bit
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bit_clear:
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dey
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dey
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dey
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next_lo_bit:
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asl
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cpy #$7f
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bcc lo_loop
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;; Now do the same for upper byte
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pla
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ldy #39 ; 8 x 5 - 1 = offset of last digit of 32768
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hi_loop:
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cmp #$7f
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bcc bit_clear_hi
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;; Bit set, so add the digits
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pha
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ldx #4
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clc
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hi_add_loop:
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lda $0100,x
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adc number_table_hi,y
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sta $0100,x
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dey
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dex
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bpl hi_add_loop
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pla
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jmp next_hi_bit
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bit_clear_hi:
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dey
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dey
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dey
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next_hi_bit:
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asl
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cpy #$7f
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bcc hi_loop
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;; Deal with any carries
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ldx #3
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carry_fix_loop:
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lda $0101,x
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cmp #9
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bcc +
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inc $0100,x
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sec
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sbc #10
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sta $0101,x
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jmp carry_fix_loop
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* dex
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bpl carry_fix_loop
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post_carry:
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;; Got digits.
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;; Skip leading zeros, and print the resulting number
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ldx #4
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* lda $0100,x
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dex
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bpl -
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;; Skip leading zeros
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ldy #0
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* lda $0100,y
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bne found_start_of_number
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iny
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cpy #4
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bne -
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found_start_of_number:
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;; Print digits
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* lda $0100,y
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ora #$30
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jsr $ffd2
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iny
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cpy #5
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bne -
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rts
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number_table_lo:
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.byte 0,0,1
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.byte 0,0,2
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.byte 0,0,4
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.byte 0,0,8
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.byte 0,1,6
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.byte 0,3,2
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.byte 0,6,4
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.byte 1,2,8
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number_table_hi:
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.byte 0,0,2,5,6
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.byte 0,0,5,1,2
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.byte 0,1,0,2,4
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.byte 0,2,0,4,8
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.byte 0,4,0,9,6
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.byte 0,8,1,9,2
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.byte 1,6,3,8,4
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.byte 3,2,7,6,8
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