==Counter/Timer Circuit==
===Informations===
The Z84C30 has four independently programmable counter/timer channels witch interface interfaced directly with the Z80 CPU. You can get full information in the CTC datasheet ([[File:Z80ctc.pdf]]).
The first thing
to consider is how those channels are linked to the CTC-AY PlayCity board.
====Channel 0 ($F880)====
The channel 0 is exclusively used to generate the frequency of the two embedded soundchips (YMZ294). The input for the trigger
==Audio Channels==
===Informations===
The CTC-AY PlayCity board is populated with two AY compatible soundchips, adding 6 stereo channels. The YMZ294 eliminate the I/O port
and improve the CPU interface through /CS, /WR control signals and a 8-bit data bus. Each sound chip can be directly
programmed using two dedicated I/O ports for registers and data. No initialization code is required.