Changes
PSG
,/* Bit 1 (Alternate) and Bit 0 (Hold) */
volume = ~volume & 0x0F if !(alternate ^ hold)
direction = 0 if hold else ~direction & 1 if alternate
When bit3 = 0, volume and direction at the end of a period always are:
volume = 0
direction = 0
=== 0Eh - External Dataregister Port A ===
