Building a Modular 6502 Computer | Ben Eater Inspired: CPU Board Design Review (Phase 3)

In this 6502 microprocessor project, I'm building a complete homebrew computer system inspired by Ben Eater's 6502 build - but with major upgrades. Learn about CPU board design, modular architecture, CPLD programming, and the engineering decisions behind creating a flexible retro computer system with modern debugging capabilities.

This project is based on Ben Eater's original 6502 design and transforms it into a fully modular system with 512K ROM, 14MHz operation, and advanced debugging features.

This video is a detailed review of the CPU board and all the support systems.

🔧 What You'll Learn:

Design philosophy: Why modular beats monolithic
Upgrading from 32K to 512K EEPROM with page registers
CPLD (Complex Programmable Logic Device) implementation
In-circuit programming without removing chips
AVR microcontroller integration for smart buffering
Planning for 12 expansion modules plus Z80 interface
Real engineering trade-offs and decision-making process

⚡ Project Specifications:

CPU: WDC 65C02 running at 1-14MHz
RAM: 32K SRAM (Cypress CY6256N-55)
ROM: 512K EEPROM (SST39SF040) with 16-page register
Control Logic: Atmel ATF1502AS CPLD
Smart Buffers: AVR64DD32 microcontrollers
12 expansion ports for modular peripherals
Advanced debugging with LCD displays and LEDs
JTAG-like functionality for step-through debugging

📍 Video Chapters:
0:00:00 Start
0:00:08 Schematic Review
0:00:35 CPLD - Complex Programmable Logic Device
0:01:23 CPLD - Standard Mode
0:02:11 Memory Map
0:02:46 Peripheral Interface Controller
0:03:43 CPLD - Programming Mode
0:04:32 CPLD - JLink Mode
0:05:59 CPLD - Address Resolution
0:07:28 CPLD - Configuration
0:08:24 CPLD - Summary
0:08:48 Power On Reset
0:11:00 Design Tips
0:12:24 Programming and Debugging the AVR
0:13:19 LED Indicators
0:15:34 Expansion Bus
0:17:05 Peripheral Select Controller
0:18:02 IRQ - Interrupt Support
0:18:42 Power Supply
0:20:14 Oscillator Section (Many options)
0:22:45 28 Mhz to 14 Mhz Conversion
0:25:17 Programmer Interface
0:25:55 Logic Analyzer Interface
0:26:47 Z80 DMA Interface

🎯 Who This Series Is For:

Retro computing enthusiasts
Electronics engineers wanting to understand computer architecture
Ben Eater fans ready for the next challenge
Makers interested in modular hardware design
Anyone who wants to understand how computers REALLY work

💡 My Teaching Philosophy:
I document failures as much as successes. My 48 years in technology have taught me that troubleshooting and debugging are the real skills worth learning. You'll see mistakes, corrections, and the thought process behind every decision.
🔗 Related Projects:
This is Part 1 of my 6502 Project Series. Future videos will cover:

Detailed schematic reviews
CPLD programming and logic design
PCB layout and assembly
Hardware testing and validation
Module development (serial, digital I/O, keyboard)
Integration with Z80 computer

📚 Tools & Software I Use:

Altium Designer for PCB design (free alternatives mentioned)
AVR64DD32 microcontrollers
Logic analyzers for debugging
Agilent/Tektronix oscilloscopes

🛠️ Background:
I started ABS Data Systems in the late 1970s after learning Intel 8080 assembly on a HeathKit H8. I've spent nearly five decades in custom software development, working in everything from assembly to C++ and C#. Now retired, I'm returning to hardware projects and sharing everything I've learned.

Ben Eater's Original 6502 Series:
https://www.youtube.com/@BenEater

Github Link to project files:
https://github.com/TerryAbs/ABSDataSystems

💬 Join the Discussion:
What features would YOU add to a homebrew computer? Drop your ideas in the comments - I read and respond to every one!
🔔 Subscribe for the complete series as I take this from concept to working computer. New videos cover PCB design, assembly, programming, testing, and inevitable troubleshooting.

Видео Building a Modular 6502 Computer | Ben Eater Inspired: CPU Board Design Review (Phase 3) канала ABS Data Systems