Microchip AY8930
This page was last modified 11:58, 9 December 2021 by Mars2000you. Based on work by Gdx and Grauw.


Microchip AY8930 chip

The Microchip Technology AY8930 EPSG is an enhanced AY-3-8910 PSG not used in MSX. Microchip Technology is an old division of General Instrument that became autonomous and continued the development of the chip. The pinout configuration is almost the same, only 2 pins (TEST1 and BC2) are no longer connected but this does not affect MSXs. The AY8930 is fully AY-3-8910 compatible at initialization.

The extended mode is activated by setting bits 7-4 of register 13 to 101x. In extended mode the following additional features are available:

  • The pulse width can be changed from square to four other duty cycles
  • There are three independent envelope generators, one for each channel
  • The amplitude control is more accurate (5 bit instead of 4 bit)
  • The tone period setting is more accurate (16 bit instead of 12 bit)
  • The noise period setting is more accurate (8 bit instead of 5 bit)
  • The noise tone can be changed by applying an AND and OR mask to the output

The Darky ePSG Stereo Card by Supersoniqs uses two AY8930 chips.

Registers by default (compatible mode)

Microchip AY8930 default registers

External links