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Routines |
| Prev: B472 | Up: Map | Next: B4A3 |
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Used by the routine at HandleMovingPortcullis.
Plays sixteen short bursts of a tone for the portcullis coming to rest. The pitches come from a random place in the first 2000 bytes of the ROM.
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Pick a random ROM address and play sixteen bursts.
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| PlayRandomNoise | B489 | LD A,($5BA5) | Fetch the second random seed from RandomSeed2. | |
| B48C | LD L,A | Use it as the low byte of a ROM address. | ||
| B48D | LD A,($5BA2) | Fetch the frame counter from FrameCounter. | ||
| B490 | AND %00011111 | Keep the lowest five bits. | ||
| B492 | LD H,A | Use it as the high byte of the ROM address. | ||
| B493 | LD E,$10 | Set the number of bursts to play. | ||
| PlayRandomNoise_NextBeep | B495 | LD A,(HL) | Fetch the next byte of the ROM. | |
| B496 | INC HL | Move on to the next one. | ||
| B497 | AND %01111111 | Keep the lowest seven bits. | ||
| B499 | LD B,A | Use it as the pitch. | ||
| B49A | LD C,$02 | Set the number of cycles of each burst. | ||
| B49C | CALL PlayWaveSequence | Play the tone. | ||
| B49F | DEC E | Decrease the burst counter and loop back to PlayRandomNoise_NextBeep until all of the bursts have been played. | ||
| B4A0 | JR NZ,PlayRandomNoise_NextBeep | |||
| B4A2 | RET | Return. | ||
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View the equivalent code in;
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