6581

Specifications

Notes

• C1 and C2 are integrating capacitors for the filter; polystyrene capacitors are preferred.
• C1 and C2 should have the same value. 2200 pF gives good operation over the audio range (30Hz-12kHz).
• Filter cutoff frequency is approx. 2.6×10^-5/C (where C is the value of C1 or C2).
• POTX and POTY pins must be connected to RC networks; the time constant RC should be 4.7×10^-4. Recommended capacitor value is 1000 pF, recommended potentiometer value is 470 kΩ.
• Maximum audio output level is approx. 3V p-p at a 6V DC level. A 1kΩ resistor should be connected from AUDIO OUT to ground, and a 1-10µF electrolytic capacitor should be used for AC coupling.
• Registers:

  $00	Voice 1 frequency low byte
  $01	Voice 1 frequency high byte
  $02	Voice 1 pulse width low byte
  $03	Voice 1 pulse width high byte (bits 3-0)
  $04	Voice 1 control (gate, sync, ring mod, waveform)
  $05	Voice 1 attack/decay rates
  $06	Voice 1 sustain level/release rate
  $07	Voice 2 frequency low byte
  $08	Voice 2 frequency high byte
  $09	Voice 2 pulse width low byte
  $0A	Voice 2 pulse width high byte (bits 3-0)
  $0B	Voice 2 control (gate, sync, ring mod, waveform)
  $0C	Voice 2 attack/decay rates
  $0D	Voice 2 sustain level/release rate
  $0E	Voice 3 frequency low byte
  $0F	Voice 3 frequency high byte
  $10	Voice 3 pulse width low byte
  $11	Voice 3 pulse width high byte (bits 3-0)
  $12	Voice 3 control (gate, sync, ring mod, waveform)
  $13	Voice 3 attack/decay rates
  $14	Voice 3 sustain level/release rate
  $15	Filter cutoff frequency low byte
  $16	Filter cutoff frequency high byte (bits 2-0)
  $17	Filter resonance/control
  $18	Filter mode/volume control
  $19	POTX value (0-255), updated every 512 clock cycles
  $1A	POTY value (0-255), updated every 512 clock cycles
  $1B	Upper 8 bits of Oscillator 3 value (random number if noise waveform is selected)
  $1C	Upper 8 bits of Voice 3 envelope generator value

• Oscillator frequency = (Fn × Fclk/16777216) Hz
• Pulse width = (PWn/40.95) %