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8255
,/* The 8255 in the CPC */
The [[8255 PPI chip]] is a general purpose input/output IC. This document will describe its role in the Amstrad CPC, CPC+ and KC compact systems. To understand its full functions please read the datasheet.
In these systems it is connected to the AY-3-8912 [[PSG|Programmable Sound Generator (PSG)]], keyboard, cassette recorder, the VSYNC of the 6845 CRTC and the "busy" signal from the parallel port.
The PPI is selected when A11 of the I/O port address is set to "0", A9 and A8 then define the PPI function access (as shown below), A15-A12 and A10 should be "1" (to prevent conflicts with other hardware), A7-A0 are don't care. So, resulting Port addresses are:
