mirror of
https://github.com/tildearrow/furnace.git
synced 2024-11-27 23:13:01 +00:00
46 lines
1.8 KiB
Markdown
46 lines
1.8 KiB
Markdown
# General Instrument AY-3-8910
|
|
|
|
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!
|
|
|
|
it is a 3-channel square/noise/envelope sound generator. the chip's powerful sound comes from the envelope...
|
|
|
|
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.
|
|
|
|
# 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
|
|
- 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.
|
|
- if `x` or `y` are 0 this will disable auto-envelope mode.
|
|
- `2Exx`: **write to I/O port A.**
|
|
- this changes the port's mode to "write". make sure you have connected something to it.
|
|
- `2Fxx`: **write to I/O port B.**
|
|
- this changes the port's mode to "write". make sure you have connected something to it.
|