furnace/doc/7-systems/5e01.md

5E01

a fantasy sound chip created by Euly, based on the Ricoh 2A03, with some improvements:

• a 37.5% duty cycle,
• 32 noise pitches instead of 16, and
• triangle channel becomes a wave channel, with four available waveforms: triangle, saw, sine and square.

effects

• 11xx: write to delta modulation counter. range is 00 to 7F.
  • this may be used to attenuate the triangle and noise channels; at 7F, they will be at about 57% volume.
  • will not work if a sample is playing.
• 12xx: set duty cycle/noise mode/waveform of channel.
  • may be 0 to 3 for the pulse channels:
    • 0: 12.5%
    • 1: 25%
    • 2: 37.5%
    • 3: 50%
  • may be 0 or 1 for the noise channel:
    • 0: long (15-bit LFSR, 32767-step)
    • 1: short (9-bit LFSR, 93-step)
  • may be 0 to 3 for the wave channel:
    • 0: triangle
    • 1: saw
    • 2: square
    • 3: sine
• 13xy: setup sweep up.
  • x is the time.
  • y is the shift.
  • set to 0 to disable it.
• 14xy: setup sweep down.
  • x is the time.
  • y is the shift.
  • set to 0 to disable it.
• 15xx: set envelope mode.
  • 0: envelope + length counter. volume represents envelope duration.
  • 1: length counter. volume represents output volume.
  • 2: looping envelope. volume represents envelope duration.
  • 3: constant volume. default value. volume represents output volume.
  • pulse and noise channels only.
  • you may need to apply a phase reset (using the macro) to make the envelope effective.
• 16xx: set length counter.
  • see NES for more information.
  • this will trigger phase reset.
• 17xx: set frame counter mode.
  • 0: 4-step.
  • 1: 5-step.
• 18xx: set PCM channel mode.
  • 00: PCM (software).
  • 01: DPCM (hardware).
  • when in DPCM mode, samples will sound muffled (due to its nature), availables pitches are limited, and loop point is ignored.
• 19xx: set triangle linear counter.
  • 00 to 7F set the counter.
  • 80 and higher halt it.
• 20xx: set DPCM frequency.
  • only works in DPCM mode.

info

this chip uses the NES instrument editor.