| The Hobbit (v1.0) | Routines |
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Decreases D, unless it would go below 0. Returns with Z set at the edge.
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| 8B26 | DEC D | x one lower | ||
| 8B27 | LD H,A | Save A for a moment | ||
| 8B28 | LD A,D | Did x wrap below 0 (become 255)? | ||
| 8B29 | CP $FF | |||
| 8B2B | LD A,H | Restore A | ||
| 8B2C | RET NZ | Still within range: done | ||
| 8B2D | INC D | Wrapped: undo the move | ||
| 8B2E | RET | Z is set, telling the caller the edge was reached | ||
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