Table of Contents
/* Imported from Wayback Machine
Original URL : https://retrobrewcomputers.org/doku.php?id=builderpages:plasmo:crc65:crc816 Snapshot date: 2025-02-12 Generator : wayback-archiver
*/
Table of Contents
CRC816, A Modified CRC65 for W65C816 CPU
Introduction
W65C816 and W65C02 share many common pin assignments such that only slight modifications to existing CRC65 pc board and the corresponding CPLD design are needed to accommodate the W65C816 CPU. This page describes the required modifications. These changes will be incorporated into next version of CRC65 so it can accommodate both W65C02 or W65C816 with a few jumper changes.
Discussion about CRC816 can be found here.
Design Information
PDF of CPLD top level schematic
Engineering Change
CRC65 has 128K RAM, but only 64K is used. A16 is currently tied to VCC. Cut trace from RAM pin31 to VCC and connect the latched data 0 to A16 (CPLD pin37) resulting in 128K of RAM.
Connect 65816 VDA (pin39) to CPLD pin 5 (formerly SDA). Cut the trace from CPLD pin 5 to SDA.
Pin 3 of CPU is unconnected currently. In W65C816 it is ABORT input, so it needs to be pulled up with a 4.7K resistor.
Connect 65816 MX output (pin38) to SDA (T3).
CRC816 Experiments
Bit bang transmitter with MX output
Bit bang WS2812 LED with MX output
See this forum discussion
This code drives the 8×8 WS2812 display as shown in the picture.
Animated GIF of the tree blinking. Software for the blinking tree
