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Routines |
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Used by the routine at GamePlay_Start.
Plays a short chirp of seven square wave cycles. The period of each cycle depends on a counter, and on the value of FrameCounter.
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| PlayChirp | 26661 | LD C,7 | Set the cycle counter to 7. | |
| PlayChirp_Loop | 26663 | LD A,C | Fetch the cycle counter. | |
| 26664 | DAA | Decimal adjust the counter, to vary the period of the cycle. | ||
| 26665 | XOR %11110000 | Flip bits 4-7. | ||
| 26667 | RLCA | Rotate A left. | ||
| 26668 | LD D,A | Put the result in D (the period). | ||
| 26669 | LD A,(24349) | Fetch the frame counter. | ||
| 26672 | RRCA | Divide by 8 (rotating the bits). | ||
| 26673 | RRCA | |||
| 26674 | RRCA | |||
| 26675 | AND %01100000 | Keep only bits 5-6. | ||
| 26677 | XOR D | Combine with the period. | ||
| 26678 | LD D,A | Update the period. | ||
| 26679 | CALL PlaySquareWave | Play a cycle using PlaySquareWave. | ||
| 26682 | DEC C | Decrease the cycle counter by one. | ||
| 26683 | JR NZ,PlayChirp_Loop | Loop back to PlayChirp_Loop until the cycle counter is zero. | ||
| 26685 | RET | Return. | ||
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