The four 8-bit audio channels each have a DMA pointer register, a data register, a frequency register, and a 6-bit volume register. Each channel has a digital-to-analog converter on the output. The four channels are grouped into a left and right audio output.
The disk controller has registers for data read, data write and control. It also contains a precompensation output circuit, and a data separator input circuit.
The serial port universal asynchronous receiver/transmitter has registers for data receive, data transmit and control.
There are four "pot ports" which are general purpose I/O pins which have counters for simple analog-to-digital conversion. They can be used to read out the position of analog joysticks.
The interrupt controller handles internal and external interrupts.
DMA request logic
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