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add POKEY documentation

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tildearrow 2022-12-20 03:19:25 -05:00
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# POKEY
a sound and input chip developed by Atari for their 8-bit computers (Atari 400, 800, XL/XE and so on). 4 channels of signature Atari sounds.
# effects
- 10xx: set waveform.
- 0: harsh noise (poly5+17)
- 1: square buzz (poly5)
- 2: weird noise (poly4+5)
- 3: square buzz (poly5)
- 4: soft noise (poly17)
- 5: square
- 6: bass (poly4)
- 7: buzz (poly4)
- 11xx: set AUDCTL. `xx` is a bitmask.
- bit 7: 9-bit poly mode. shortens noise.
- bit 6: high channel 1 clock (~1.79MHz on NTSC).
- overrides 15KHz mode.
- bit 5: high channel 3 clock (~1.79MHz on NTSC).
- overrides 15KHz mode.
- bit 4: join channels 1 and 2 for a wide period range.
- use with conjunction with bit 6.
- channel 2 becomes inaccessible when this is on.
- bit 3: join channels 3 and 4 for a wide period range.
- use with conjunction with bit 5.
- channel 4 becomes inaccessible when this is on.
- bit 2: high-pass filter (channels 1 and 3).
- filtered output on channel 1 (I suggest you to set channel 3 volume to 0).
- use for PWM effects (not automatic!).
- bit 1: high-pass filter (channels 2 and 4).
- filtered output on channel 2 (I suggest you to set channel 4 volume to 0).
- use for PWM effects (not automatic!).
- bit 0: 15KHz mode.