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furnace/doc/7-systems/5e01.md
tildearrow c6a9277d51 document chip options
2024-07-06 14:52:07 -05:00

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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.

chip config

the following options are available in the Chip Manager window:

  • Clock rate: sets the rate at which the chip will run.
  • DPCM channel mode: allows you to set which mode to use for the DPCM channel.
    • DPCM: the default mode, playing 1-bit DPCM samples as supported by the hardware.
    • PCM: this mode provides crispier samples by writing the delta counter directly. uses a lot of CPU time in console.