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Routines |
| Prev: 72CA | Up: Map | Next: 72F2 |
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Used by the routine at UpdateBeams.
Plays the noise of a beam, using clicks that depend on the first three bytes of the object of the beam.
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| PlayBeamSound | 72CF | LD A,(IX+$00) | Read offset 00 of IX. | |||||
| 72D2 | XOR (IX+$01) | Flip the bits of A that are set in the byte at offset 01 of IX. | ||||||
| 72D5 | AND %00001111 | Keep the bits of A that are set in 0F. | ||||||
| 72D7 | ADD A,$08 | Add 08 to A. | ||||||
| 72D9 | LD C,A | That is the number of clicks in the beam. | ||||||
| 72DA | LD A,(IX+$02) | Read offset 02 of IX. | ||||||
| 72DD | AND %00011111 | Keep the bits of A that are set in 1F. | ||||||
| 72DF | LD E,A | The third byte is the click pattern. | ||||||
| PlayBeamSound_Loop | 72E0 | LD A,C | Mix the clicks still left with the pattern. | |||||
| 72E1 | ADD A,E | A gains E. | ||||||
| 72E2 | AND %00001111 | Keep the bits of A that are set in 0F. | ||||||
| 72E4 | ADD A,A | Double the mixed value. | ||||||
| 72E5 | LD B,A | Keep it as the on-time. | ||||||
| 72E6 | LD A,E | The off-time starts from the pattern. | ||||||
| 72E7 | ADD A,B | A gains B. | ||||||
| 72E8 | ADD A,A | Double the sum. | ||||||
| 72E9 | SUB B | Subtract B from A. | ||||||
| 72EA | LD D,A | That is the off-time of this click. | ||||||
| 72EB | CALL MakeClick | Call MakeClick. | ||||||
| 72EE | DEC C | One click of the beam has been played. | ||||||
| 72EF | JR NZ,PlayBeamSound_Loop | Jump to PlayBeamSound_Loop if the zero flag is clear. | ||||||
| 72F1 | RET | Return. | ||||||
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