Port space addressing is straightforward. If upper address bit 7 is set, value is written to chip address register. If address bit 6 is set, value is written (or read) to chip register last addressed.
|40p||AY_DATA||Read/write the selected AY internal register|
|80pw||AY_ADDR||Write here to select AY internal register|
There is a capacitor filter control network controlled through memory addresses decoded from 6000. Reading from an address sets the filter as follows:
aa, bb, cc are AY chip 0 voices
dd, ee, ff are AY chip 1 voices (not used in this 1-chip hardware)
For each voice the two-bit data switches capacitors as follows:
11 0.047uF + 0.220uF