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C64 I/O Board Pages
Project Description
C64 I/O Board Drawings
C64 Exp. Board Notes
Card Edge Connector
Component Layout
LED Bar & LED Drivers
Printer Port Pinout
Reset & Phi-2 Circuits
Short C64 Test Program
C64 I/O Expansion Board Pages: Project Description

This is an expansion board I made for our son to use with the Commodore 64 to interface to his model railroad setup or whatever he wanted. Main I/O is through two 26-pin headers. The DB-25 at the end is for a printer. The board has two 6522's. Unfortunately, since the 6522 needs the CS lines valid before its phase 2 goes up and the C64 doesn't meet that requirement, I had to put in a circuit to delay the rising edge of phase 2 but not the falling edge. Since the C64 lacks a reset button, I put one at the top left. The LEDs are driven by buffers to show the status on VIA1PB without loading it down.

Here's the wire-wrap side of the same board.

Since the issue of using the 6522 with a C64 has been raised before on the forum, here's the notebook page on how that works.




Last updated September 13, 2003.