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Routines |
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Used by the routine at NextEntity.
Plays the engine sound: four square waves using PlaySquareWave. The period of the waves is 3F minus the speed divided by 04 so the faster the car is going, the higher the pitch. There is no sound when the car is stationary.
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| SoundsEngine | 6158 | LD A,($5E0D) | Fetch the speed of the car from Speed. | |
| 615B | AND A | Return if the car is stationary. | ||
| 615C | RET Z | |||
| 615D | RRCA | Divide the speed by 04 by rotating it right twice. | ||
| 615E | RRCA | |||
| 615F | CPL | Flip the bits, so the faster the car the shorter the period. | ||
| 6160 | AND %00111111 | Keep only bits 0-5. | ||
| 6162 | LD D,A | Set the period of the waves. | ||
| 6163 | LD C,$04 | Set the wave counter to 04. | ||
| 6165 | LD A,($5E80) | If Entity_Player is 03 then jump to SoundsEngine_Loop. | ||
| 6168 | CP $03 | |||
| 616A | JR Z,SoundsEngine_Loop | |||
| 616C | LD B,$0C | Set the delay counter to 0C (this has no effect, as it is overwritten). | ||
| SoundsEngine_Loop | 616E | CALL PlaySquareWave | Play a square wave using PlaySquareWave. | |
| 6171 | DEC C | Decrease the wave counter by one and loop back to SoundsEngine_Loop until all 04 waves have been played. | ||
| 6172 | JR NZ,SoundsEngine_Loop | |||
| 6174 | RET | Return. | ||
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