Last active
August 17, 2025 09:34
-
-
Save formicant/f4226fbbb39588ddf7ea1fb65e2df11c to your computer and use it in GitHub Desktop.
Z80 word to BCD
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| ; Converts a two-byte value to BCD | |
| ; Works in const time, no jumps | |
| ; params: `hl` - word value | |
| ; return: `ahl` - 5 digits in BCD | |
| ; spoils: `f`, `c` | |
| ; time: 454, length: 112 | |
| wordToBcd: | |
| IFUSED | |
| ; double dabble algorithm | |
| xor a | |
| DUP 3 | |
| sla h | |
| adc a | |
| EDUP | |
| DUP 3 | |
| sla h | |
| adc a : daa | |
| EDUP | |
| sla h | |
| DUP 2 | |
| adc a : daa | |
| rl h | |
| EDUP | |
| sla l | |
| adc a : daa | |
| rl h | |
| sla l | |
| adc a : daa : ld c, a | |
| ld a, h : adc a : daa : ld h, a | |
| DUP 2 | |
| sla l | |
| ld a, c : adc a : daa : ld c, a | |
| ld a, h : adc a : daa : ld h, a | |
| EDUP | |
| sla l | |
| DUP 4 | |
| ld a, c : adc a : daa : ld c, a | |
| ld a, h : adc a : daa : ld h, a | |
| rl l | |
| EDUP | |
| ld a, l : ld l, c | |
| ret | |
| ENDIF |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment