Sunsoft 5B audio

The Sunsoft 5B is a superset of the Sunsoft FME-7. It is identical to the FME-7 except it contains extra audio hardware. This audio hardware was only used in one game, Gimmick!

Registers

The audio hardware is a type of the General Instrument AY-3-8910 PSG, or Yamaha's YM2149F variant.

Audio Register Select ($C000)

7......0
----RRRR
    ++++- The 4-bit internal register to select for use with $E000

Audio Register Write ($E000)

7......0
VVVVVVVV
++++++++- The 8-bit value to write to the internal register selected with $C000

Internal audio registers

The AY-3-8910 has 16 internal audio registers, selected with $C000 and written to with $E000.

Register	Bitfield	Description
$00	LLLL LLLL	Channel A low period
$01	---- HHHH	Channel A high period
$02	LLLL LLLL	Channel B low period
$03	---- HHHH	Channel B high period
$04	LLLL LLLL	Channel C low period
$05	---- HHHH	Channel C high period
$06	---P PPPP	Noise period
$07	--CB Acba	Noise enable on channels C/B/A, Tone enable on channels c/b/a
$08	--EV VVVV	Channel A envelope enable (E), volume (V)
$09	--EV VVVV	Channel B envelope enable (E), volume (V)
$0A	--EV VVVV	Channel C envelope enable (E), volume (V)
$0B	LLLL LLLL	Envelope low period
$0C	---- HHHH	Envelope high period
$0D	---- CAaH	Envelope shape: continue (C), attack (A), alternate (a), hold (H)
$0E	---- ----	I/O port A (unused)
$0F	---- ----	I/O port B (unused)