The ET-3400 was a microprocessor trainer kit sold in the 70's and 80's and was designed to be assembled by the end user and was used to teach fundamentals of microprocessors.

The kit had the following features:
  • Motorola 6800 8-bit CPU clocked at 1MHz
  • Six 7-segment LED displays used to display address and data information, and as a visual output device
  • 17 push-button switches for the hex keypad
  • 8 LEDs for general purpose visual output
  • an 8-bit DIP switch for data input
  • a 1 KB ROM containing the Monitor program
  • 256 bytes RAM
  • buffered 8-bit data and 16-bit address lines, exposed through breadboard connectors.

The ROM contained a program allowing the user to enter programs using the keypad. Programs were entered in machine code as hexadecimal and stored in RAM. The user could then execute the program, or step through it and view and modify registers.

Through the exposed data and address buses, it was possible to extend the capabilities of the kit by adding peripherals such as an LCD display. The kit had a breadboard where the user could wire up semiconductor devices to learn about microprocessor basics such as logic gates and addressing.

This project aims to emulate the basic features of the ET-3400. Although initially built from scratch, the 6800 CPU emulator core now contains code from the MAME project in order to be more accurate.



The main window contains the display and keypad.

The keypad accepts mouse clicks. The keyboard is also mapped to the keypad. Pressing on the key on the keyboard (0-9, A-F) will simulate a press on the corresponding key on the keypad. Pressing Escape on the keyboard will simulate Reset.

You can download the trainer's Manual here.

Loading S19 format files

The emulator supports S19 format files. Click File > Load and select your .s19 or .obj file to load it into memory. The program will be loaded into RAM at $0000.

The download and source contains the HeathKit manual sample program listings in S19 format. See the README.txt file under the samples directory for instructions on how to load and execute the sample files.

Quick ET-3400 Guide

ACCA - View contents of Accumulator A Register
ACCB - View contents of Accumulator B Register
PC - View contents of Program Counter Register
INDEX - View contents of Index Pointer Register
CC - View contents of Condition Codes Register
SP - View contents of Stack Pointer Register
RTI - Return from Interrupt
SS - Single Step
BR - Break
AUTO - Start entering hex at specified address
BACK - During EXAMine mode, move address back
CHAN - During EXAMine mode, edit hex at specified address. During ACCA/ACCB/PC mode, edit hex in selected register
DO - Execute RAM at given address
EXAM - Start viewing hex at specified address
FWD - During EXAMine mode, move address forward

Last edited Aug 20, 2014 at 9:46 AM by RupertAvery, version 17