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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 63 minus the speed divided by 4 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 | 24920 | LD A,(24077) | Fetch the speed of the car from Speed. | |
| 24923 | AND A | Return if the car is stationary. | ||
| 24924 | RET Z | |||
| 24925 | RRCA | Divide the speed by 4 by rotating it right twice. | ||
| 24926 | RRCA | |||
| 24927 | CPL | Flip the bits, so the faster the car the shorter the period. | ||
| 24928 | AND %00111111 | Keep only bits 0-5. | ||
| 24930 | LD D,A | Set the period of the waves. | ||
| 24931 | LD C,4 | Set the wave counter to 4. | ||
| 24933 | LD A,(24192) | If Entity_Player is 3 then jump to SoundsEngine_Loop. | ||
| 24936 | CP 3 | |||
| 24938 | JR Z,SoundsEngine_Loop | |||
| 24940 | LD B,12 | Set the delay counter to 12 (this has no effect, as it is overwritten). | ||
| SoundsEngine_Loop | 24942 | CALL PlaySquareWave | Play a square wave using PlaySquareWave. | |
| 24945 | DEC C | Decrease the wave counter by one and loop back to SoundsEngine_Loop until all 4 waves have been played. | ||
| 24946 | JR NZ,SoundsEngine_Loop | |||
| 24948 | RET | Return. | ||
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