The C64 Link232+ Project Page

Introduction

Welcome to the C64 Link232+ Project Page! The Link-232 is an RS-232 cartridge for the C64 created by Jim Brain. It was done in Eagle. This project is my attempt to clone it in Kicad and to make it smaller by substituting the two MAX232 chips with one MAX238 chip. Also, I may incorporate this schematic, or a variation, in another project.

Theory of Operation

The Link232 uses the 6551 ACIA as the main communication chip. It puts out TTL level signals that are converted to RS-232 standard voltages via the MAX238. The MAX238 has 4 inputs and 4 outputs so it can replace two MAX232 chips. There is a jumper to select if the 6551 chip uses IO1 or IO2 address space. A 74LS138 3-to-8 decoder allows you to map the 6551 chip at any one of 8 address ranges within the selected IO area. Finally there is a jumper to select whether the 6551 uses NMI or IRQ to signal the C64.

Schematics and PCB

Here is the current schematic diagram and PCB:

Status

Kicad was used to design the board. The schematics are complete. The parts are arranged and routed. PCB's have arrived! A board has been built and being tested.

Project History

2016-09-04: Initial design - 6551, MAX238, DB-9 mounted on board. Schematic duplicated, parts placed and routed. Board size set.
2016-09-05: Initial Web page. Switched DB9 to male, so needed to re-route some traces. Added labelling and fixed component reference labels.
2016-09-13: Slight reduction of board length due to shuffled components. Cleaned up and added labels. Optimized routing.
2016-10-03: PCB's have been ordered!
2016-10-04: PCB's are at the board house now. Wow, that was fast!
2016-10-09: PCB's have been shipped.
2016-11-02: PCB's have arrived!
2016-11-04: PCB has been assembled and is being tested.

Thank-You's

Thanks to Jim Brain for providing schematics for his Link232 board!

Contact

Page Created: Sep 5/2016. Last updated: Nov 7/2016, 11:00pm EST

Send comments or feedback to Steve Gray(sjgray@rogers.com)