From 15afb1da84468d2824259125ce086b8ed9483eb4 Mon Sep 17 00:00:00 2001 From: tildearrow Date: Tue, 20 Dec 2022 03:19:25 -0500 Subject: [PATCH] add POKEY documentation --- papers/doc/7-systems/pokey.md | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) create mode 100644 papers/doc/7-systems/pokey.md diff --git a/papers/doc/7-systems/pokey.md b/papers/doc/7-systems/pokey.md new file mode 100644 index 00000000..b05c4367 --- /dev/null +++ b/papers/doc/7-systems/pokey.md @@ -0,0 +1,34 @@ +# 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.