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Routines |
| Prev: 57888 | Up: Map | Next: 57990 |
| 57947 | LD A,14 | Playing area is 14 character rows high | ||
| 57949 | LD (60103),A | |||
| 57952 | LD DE,16450 | Screen display address for top left of playing area | ||
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Clear a character row (8 pixels) of the playing area:
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| 57955 | LD C,8 | 8 pixel rows | ||
| 57957 | LD H,D | Copy screen display address from DE to HL | ||
| 57958 | LD L,E | |||
| 57959 | LD B,28 | 28 character rows to clear | ||
| 57961 | LD (HL),0 | Clear pixel byte | ||
| 57963 | INC L | Move on character square right | ||
| 57964 | DJNZ 57961 | Repeat for 28 character rows | ||
| 57966 | INC H | Move down 1 pixel | ||
| 57967 | DEC C | |||
| 57968 | JR NZ,57958 | Repeat for 8 pixel rows | ||
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Move down to next (character) row:
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| 57970 | LD A,E | Get starting left hand position | ||
| 57971 | ADD A,32 | Move down to next character square | ||
| 57973 | LD E,A | Are we crossing a third-of-screen boundary? | ||
| 57974 | JR NC,57980 | |||
| 57976 | LD A,D | If so, recalculate screen display high-byte accordingly | ||
| 57977 | ADD A,8 | |||
| 57979 | LD D,A | Store corrected screen address high byte back in D register | ||
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Check if all character rows have been cleared:
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| 57980 | LD A,(60103) | Get character row counter | ||
| 57983 | DEC A | ...and decrement | ||
| 57984 | LD (60103),A | |||
| 57987 | JR NZ,57955 | Repeat for all 14 character squares of playing area | ||
| 57989 | RET | |||
| Prev: 57888 | Up: Map | Next: 57990 |