Zon ZX-81 Programmable Sound Generator expansion for ZX81PLUS35 with working SD-Card

Project ZON X-81 for ZX81+35
Programmable sound generator for my ZX81 clone
Status	In progress
Contact	Mahjongg
Last Update	2016-06-23

The ZON X-81 is a sound generator based on the famous AY-3-8912 PSG.

This is a remake for my ZX-81+35 clone. It features stereo sound outputs, and also enables the GPIO's, to which an SD-card slot is connected, which hopefully will enable, with help of some software expansion in ROM, to read SD-cards. Adittionally the board serves (can serve) as an interface to a classical edge connector, or to another ZX81+35 expansion board (with pinheader connector).

I started by investigating the original ZON X-81, and soon found out there were two verslons, the original ZON X-81 and the later, "Spectrum compatible" ZON X. For neither a schematic diagram seemed to be available, and there seemed to be some confusion about the I/O ports used. In the end I decided the best course of action seemed to be to use the available information to draw up my own schematic, and ask for input from the community. So I eventually came up with this. File:ZONX sound expansion REV 2,0.pdf