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A Most Very Unofficial Guide to the W65C265SXB

The W65C265SXB ("265SXB" for short) is an engineering development board produced -- basically a single-board computer in the same sense as the Raspberry Pi -- by the Western Design Center (WDC). It is based on the W65C265S microcontroler, which in turn has a 65816 MPU at its core -- the 8/16-bit hybrid "big sibling" of the famous 6502 MPU that powered classic computers such as the VIC-20 and Apple II. Because of the hybrid nature of the 65816, the 265SXB is pretty much the simplest way to get started with a 6502 system.

This document is an unofficial guide to setting up, programming, expanding, and using the 265SXB. It supplements the official documentation provided by WDC.


First Steps

Overview: What's in the box.
Setup: Getting the 265SXB up and running.
First Programs: Simple things to do with the 265SXB right out of the box.
Uploading Programs: How to enter and/or upload programs to the 265SXB.


Memory: Out of the box configuration, how chip select signals are generated.
Flash: How to install, select a bank, and erase and program the flash memory chip under software control.
Serial Lines: Connecting USB serial adapters to the serial lines of the 265SXB.


WDC Tools: Installing and working with the WDC development packages.
The Monitor: Using the built-in Mensch Monitor program, a miniature operating system.
Clock and Timers: Using the built-in clock functions.

Projects and Expansions

Expansions: Expansion boards, also known as "daughter boards" or shields.


Link list: Useful links.
Erratum: List of known errors in the Manual and bugs in the Mensch Monitor ROM listing.


Various members of the Forum contributed to this document and gave invaluable advice.


No liability for the contents of these documents can be accepted. Use the concepts, examples and information at your own risk. There may be errors and inaccuracies that could be damaging to your system. The author(s) take no responsibility for damage resulting.

All copyrights are held by their by their respective owners, unless specifically noted otherwise. Use of a term in this document should not be regarded as affecting the validity of any trademark or service mark. Naming of particular products or brands should not be seen as endorsements.