Created
January 16, 2016 04:50
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Some code I used for doing decimal <-> hex conversions in my Apple IIgs memory testing app. This is actually straight 6502 code. Max int $FFFF.
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| * x/y = high/low | |
| BINtoBCD stx BIN | |
| sty BIN+1 | |
| jsr BINBCD16 | |
| ldx BCD | |
| ldy BCD+1 | |
| rts | |
| BCDtoBIN | |
| stx BCD | |
| sty BCD+1 | |
| jsr BCDBIN16 | |
| ldx BIN | |
| ldy BIN+1 | |
| rts | |
| BIN dw $0000 | |
| BCD ds 3 | |
| BINBCD16 SED ; Switch to decimal mode | |
| LDA #0 ; Ensure the result is clear | |
| STA BCD+0 | |
| STA BCD+1 | |
| STA BCD+2 | |
| LDX #16 ; The number of source bits | |
| CNVBIT ASL BIN+0 ; Shift out one bit | |
| ROL BIN+1 | |
| LDA BCD+0 ; And add into result | |
| ADC BCD+0 | |
| STA BCD+0 | |
| LDA BCD+1 ; propagating any carry | |
| ADC BCD+1 | |
| STA BCD+1 | |
| LDA BCD+2 ; ... thru whole result | |
| ADC BCD+2 | |
| STA BCD+2 | |
| DEX ; And repeat for next bit | |
| BNE :CNVBIT | |
| CLD ; Back to binary | |
| rts | |
| * 16-bit mode!!! | |
| BCDBIN16 | |
| clc | |
| xce | |
| rep #$30 | |
| stz BIN | |
| lda BCD | |
| and #$000F ;get 1's | |
| sta BIN | |
| lda BCD | |
| and #$00F0 ;get 10's | |
| lsr | |
| lsr | |
| lsr | |
| lsr | |
| jsr TIMES10 | |
| clc | |
| adc BIN ;add 10's back to BIN | |
| sta BIN | |
| lda BCD | |
| and #$0f00 ;get 100's | |
| xba | |
| jsr TIMES10 | |
| jsr TIMES10 | |
| clc | |
| adc BIN | |
| sta BIN | |
| lda BCD | |
| and #$f000 ;get 1000's | |
| xba | |
| lsr | |
| lsr | |
| lsr | |
| lsr | |
| jsr TIMES10 | |
| jsr TIMES10 | |
| jsr TIMES10 | |
| clc | |
| adc BIN | |
| sta BIN | |
| sep #$30 | |
| rts | |
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