https://github.com/michael-0acf4/asac
A Simple Audio Chip (ASAC)
https://github.com/michael-0acf4/asac
assembler audio circuit-diagram logisim logisim-evolution midi toy-computer
Last synced: 10 months ago
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A Simple Audio Chip (ASAC)
- Host: GitHub
- URL: https://github.com/michael-0acf4/asac
- Owner: michael-0acf4
- License: mit
- Created: 2025-07-27T19:21:32.000Z (11 months ago)
- Default Branch: main
- Last Pushed: 2025-08-06T23:28:46.000Z (10 months ago)
- Last Synced: 2025-08-06T23:31:08.279Z (10 months ago)
- Topics: assembler, audio, circuit-diagram, logisim, logisim-evolution, midi, toy-computer
- Homepage:
- Size: 441 KB
- Stars: 1
- Watchers: 0
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# asac
A Simple Audio Chip (ASAC) is a simple chip in which we can write programs that
mimics the [MIDI format](https://en.wikipedia.org/wiki/MIDI).
- Supports 4 channels
- Each instruction takes exactly 1 clock cycle except `WAIT` (expands into
multiple `NOOP`).
# Demo
[ASAC v1 | Gate Of Steiner (loud alert)](http://www.youtube.com/watch?v=_kRC-5GoDq0 "ASAC v1 | Gate Of Steiner (loud alert)")
[](http://www.youtube.com/watch?v=_kRC-5GoDq0 "ASAC v1 | Gate Of Steiner (loud alert)")
# "Hello World" example
```asm
LABEL start
NOTEON 1 65 100
WAIT 2
NOTEOFF 1 65
NOTEON 2 66 100
WAIT 2
NOTEOFF 2 66
NOTEON 3 67 100
WAIT 2
NOTEOFF 3 67
NOTEON 4 68 100
WAIT 2
NOTEOFF 4 68
JUMP start
```
I have not planned on adding conditional jumps (as in jump when note on channel
X is on/off) yet. This is purely intented as a simple target for simple audio
descriptions such as the MIDI format or most
[DAW](https://en.wikipedia.org/wiki/Digital_audio_workstation).
# Notes
There are 128 addressable audio output (0 to 127), the frequency follows:
$$f(i) = 440 Hz \times 2^{(i-69)/12}$$
# Instruction Set
```
8 bit 8 bits 8bits 8 bits
NOTEON [chan] [ note 0-127 ][ vel ]
NOTEOFF [chan]
WAIT [ delay ]
JUMP [ label ]
NOOP
```
# Microcode Spec
```
microcode
opcode
0x00: 0x28 (0b00101000) => pick chan 1, unset
0x01: 0x29 (0b00101001) => pick chan 2, unset
0x02: 0x2a (0b00101010) => pick chan 3, unset
0x03: 0x2c (0b00101100) => pick chan 4, unset
0x04: 0x38 (0b00111000) => pick chan 1, set
0x05: 0x39 (0b00111001) => pick chan 2, set
0x06: 0x3a (0b00111010) => pick chan 3, set
0x07: 0x3c (0b00111100) => pick chan 4, set
^^^
||+ -- enable
|+ --- on/off speaker
+----- set kind flag (always 0 on other micro-instructions)
0x08: 0xde (0b11011110) => wait by 'value' amount
0x09: 0x42 (0b01000010) => jump to 'value' addr
```