furnace/doc/7-systems/ay8910.md

58 lines
2.6 KiB
Markdown
Raw Normal View History

2022-01-16 06:10:43 +00:00
# General Instrument AY-3-8910
2022-03-26 18:55:20 +00:00
this chip was used in many home computers (ZX Spectrum, MSX, Amstrad CPC, Atari ST, etc.), video game consoles (Intellivision and Vectrex), arcade boards and even slot machines!
2022-01-16 06:10:43 +00:00
2022-10-16 05:53:05 +00:00
it is a 3-channel square/noise/envelope sound generator. the chip's powerful sound comes from the envelope...
2022-01-16 06:10:43 +00:00
2022-10-16 05:53:05 +00:00
the AY-3-8914 variant was used in Intellivision, which is pretty much an AY with 4 level envelope volume per channel and different register format.
2023-07-11 18:26:43 +00:00
as of Furnace 0.6pre7, AY-3-8910 supports software sample playback, where all 3 channels can play 4-bit PCM samples (at the cost of a very high CPU usage)
2023-07-09 12:07:19 +00:00
2022-01-16 06:10:43 +00:00
# effects
- `20xx`: **set channel mode.**
- `0`: square
- `1`: noise
- `2`: square and noise
- `3`: envelope
- `4`: envelope and square
- `5`: envelope and noise
- `6`: envelope and square and noise
- `7`: nothing
- `21xx`: **set noise frequency.** range is `0` to `1F`.
- `22xy`: **set envelope mode.**
- `x` sets the envelope shape:
- `0`: `\___` decay
- `4`: `/___` attack once
- `8`: `\\\\` saw
- `9`: `\___` decay
- `A`: `\/\/` inverse obelisco
- `B`: `\¯¯¯` decay once
- `C`: `////` inverse saw
- `D`: `/¯¯¯` attack
- `E`: `/\/\` obelisco
- `F`: `/___` attack once
2022-01-16 06:10:43 +00:00
- if `y` is 1 then the envelope will affect this channel.
- `23xx`: **set envelope period low byte.**
- `24xx`: **set envelope period high byte.**
- `25xx`: **slide envelope period up.**
- `26xx`: **slide envelope period down.**
- `29xy`: **enable auto-envelope mode.**
- in this mode the envelope period is set to the channel's notes, multiplied by a fraction.
- `x` is the numerator.
- `y` is the denominator.
2022-03-26 18:55:20 +00:00
- if `x` or `y` are 0 this will disable auto-envelope mode.
- `2Exx`: **write to I/O port A.**
2022-03-27 01:55:43 +00:00
- this changes the port's mode to "write". make sure you have connected something to it.
- `2Fxx`: **write to I/O port B.**
2022-10-16 05:53:05 +00:00
- this changes the port's mode to "write". make sure you have connected something to it.
2023-07-09 12:42:48 +00:00
# chip config
## AY derivative modes
2023-07-11 18:27:21 +00:00
AY-3-810 was an absurdly popular chip that was blessed with many third-party clones, licensed or not.
2023-07-09 12:42:48 +00:00
- the AY-3-8914 variant was used in Intellivision, which is pretty much an 8910 with 4 level envelope volume per channel and different register format.
2023-07-14 09:16:36 +00:00
- Yamaha YM2149 was an AY-3-8910 clone released in 1983. it's almost identical to AY with minor differences being: higher hardware envelope step resolution (16 vs 32), half-clock mode when voltage level is low, much stronger DC offset and cleaner, but softer output.
2023-07-09 12:42:48 +00:00
- Sunsoft 5B is YM2149 clone with half-clock mode forced on.