asac

A Simple Audio Chip (ASAC) is a simple chip in which we can write programs that mimics the MIDI format.

• Supports 4 channels
• Each instruction takes exactly 1 clock cycle except WAIT (expands into multiple NOOP).

Demo

ASAC v1 | Gate Of Steiner (loud alert)

"Hello World" example

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.

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