149 lines
2.8 KiB
ArmAsm
149 lines
2.8 KiB
ArmAsm
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; Based on BSM (Bit Shifter's Monitor)
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Get_Addr_To_LAC:
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phx
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phy
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phz
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lda #$00
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sta Dig_Cnt ; count columns read
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sta Long_AC+0 ; clear result Long_AC
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sta Long_AC+1
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sta Long_AC+2
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sta Long_AC+3
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jsr Get_Glyph ; get 1st. character
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+beq @exit
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ldy #$03 ; here we allow '$', '+', '&', and '%' prefixes
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@loop_prefix:
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cmp Cons_Prefix,Y ; Y = base index
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beq @valid_prefix ; -> valid prefix
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dey
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bpl @loop_prefix
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iny ; Y = 0
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dec Buf_Index
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@valid_prefix:
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; at this point .Y value determines a numeric system
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jsr Get_Char
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beq @exit ; '?', ':'', ';' and zero terminate
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cmp #'0'
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bcc @exit
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cmp #':'
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bcc @valid_digit ; 0-9
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cmp #'A'
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bcc @exit
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cmp #'G'
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bcs @exit
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sbc #$07 ; hex conversion
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@valid_digit:
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sbc #'0'-1
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cmp Num_Base,Y
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+bcs Mon_Error ; branch if digit above numerical system limit
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pha ; push digit to the stack
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inc Dig_Cnt
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cpy #$01
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bne @laba ; branch if not decimal
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ldx #$03 ; decimal - push Long_AC
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@push_long_AC:
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lda Long_AC,X
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pha
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dex
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bpl @push_long_AC
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tsx ; double pushed value
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asl STACK+1,X
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rol STACK+2,X
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rol STACK+3,X
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rol STACK+4,X
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+bcs Mon_Error ; branch if overflow
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@laba:
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ldx Num_Bits,Y ; multiply Long_AC by power of 2 (depending on numeric system)
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@shift:
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asl Long_AC+0
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rol Long_AC+1
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row Long_AC+2
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+bcs Mon_Error ; overflow
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dex
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bne @shift
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cpy #$01 ; decimal adjustment
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bne @add_digit ; branch if not a decimal number
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ldx #$00
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ldz #$03
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clc
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@pull_and_add:
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pla
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adc Long_AC,X
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sta Long_AC,X
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inx
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dez
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bpl @pull_and_add
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@add_digit:
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pla ; pull digit
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clc
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adc Long_AC+0
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sta Long_AC+0
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bcc @valid_prefix
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inc Long_AC+1
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bne @valid_prefix
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inw Long_AC+2
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bne @valid_prefix
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jmp Mon_Error ; number foo large
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@exit:
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lda Long_AC+3
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and #%11110000
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+bne Mon_Error ; MEGA65 has a 28-bit address bu
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lda Dig_Cnt ; check if we should enable long addressing mode
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cmp Num_Limit,Y
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bcc @check_done
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cpy #$1
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bne @set_long_mode
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lda Long_AC+2 ; for decimal system check most significant bytes instead
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ora Long_AC+3
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beq @check_done
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@set_long_mode:
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lda #$80 ; set addressing mode to long
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sta Addr_Mode
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@check_done:
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lda Dig_Cnt
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plz
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ply
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plx
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cmp #$00 ; allow to easily check if a parameter was given
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rts
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