---
title: Overview
description: "TommyPROM Arduino based programmer for 28C256 EEPROMs"
has_children: false
nav_order: 1
---

# TommyPROM - An Arduino-based EEPROM programmer

This is a simple EEPROM programmer and reader that can be assembled using an Arduino and a
few additional parts.  It has been successfully built using the Arduino UNO, Nano and
Boarduino models.

The original code was specific to the 28C256 32Kx8 EEPROM, but it has been extended to also support Intel 8755A EPROMS and some 29C010 Flash.

![TommyPROM Nano Hardware](images/TommyPROM-nano.jpg)

## Design

The 28C design can be used with other 5V EEPROMS as well. Many 5V chips, including UV
EPROMs, such as the 2716, 2764, 27C2001 and 27C040, can be read, but not written, with the
basic hardware. Some pin changes may be needed to get the signals to the correct pins on
the device.  See the [Extending the design](extending) page for details on suggested
hardware and software changes needed to support new EPROM and EEPROM families.

The PROM-specific code is modular and can be easily adapted to support additional devices.
There are currently drivers and hardware designs for 28C series EEPROMS and the Intel
8755A EPROM.

Some 29C series chips, like the 29C010 can be written with the 28C hardware. The 29C
series only differs from the 28C in that the 29C chips erase and write an entire sector at
a time.  The 29C010 and some 29C020 chips use a 128 byte sector, which matches the XModem
buffer in the current code.  Other 29C020s and all 29C040s use a 256 byte sector and
cannot be written without code changes to buffer up an entire 256 byte block of data
before writing.

Features include:
* Simple hardware design that can be assembled on a breadboard.
* ROM images transfers using XMODEM - no special host client needed.
* Support for fast block EEPROM writes - a 32K EEPROM will program in just a few seconds.
* Optimized code that supports the timing requirements needed to unlock the 28C series Software Protection Algorithm.
* Modular software design to easily support other EEPROM and EPROM families.

The [hardware](hardware) page has descriptions of the hardware designs and links to schematics.  The [software](software) page has class definitions and more information
on the software design.

The project was inspired by the
[MEEPROMMER programmer](http://www.ichbinzustaendig.de/dev/meeprommer-en).

## Compiling

Open the TommyPROM.ino file in the Arduino IDE. It should automatically open the cpp and h
files as well. The default code programs 28C series chips using Arduino Nano hardware.  To
use this version, just compile and upload it to the Arduino.

**Note well** that this code has been optimized for the Aduino UNO and Nano hardware so
that it can run quickly enough to meet 28C series chip timing requirements for SDP
unlocking.  To use different Arduino hardware, like the Micro, the board-specific code in
PromDevice.cpp and PromAddressDriver.cpp must be change to match the port mappings between
the ATmega chip and the Arduino I/O pins.

To use the 8755A version of the code and matching hardware, uncomment PROM_IS_8755A and
comment out the other PROM_IS_xx choices in Configure.h.

## Operation
![TommyPROM Screenshot](images/tp05.png)

To use the programmer, connect the Arduino USB to the host computer and run a terminal
program, such as TeraTerm (Windows) or Minicom (Linux).  The Arduino development Serial
Monitor can also be used as a terminal initially, but it does not support XMODEM
transfers, so the READ and WRITE commands can't be used.

Set the terminal's serial parameters to 115200 baud, 8 bits, no parity, 1 stop bit to
match the Arduino.  Press the Enter key.  If the connection is successful, TommyPROM will
display a menu of options.

Most of the commands take a start address parameter, always entered as 1 to 5 hex
characters.  Leading zeros are not required. If needed, the end address parameter is also
in hex.  Parameters are separated by a space. For example, either of the commands:

    d0000 01ff
    d0 1ff

will dump memory from 0000H to 01ffH.  Note that commands and parameters can be entered in
uppercase or lowercase.

The R command is used to read from a PROM and save a binary image on the host.  The W
command receives a file from the host and writes (burns) it into the device.  The R
command needs a start and end address.  The W command determines the end address from the
received file size.

The READ and WRITE commands both use XMODEM CRC to complete the file transfers.  Many
terminal programs default to XMODEM Checksum format, so be sure to select XMODEM CRC as
the format. Once the READ or WRITE command is issued to the programmer, the transfer must
be started on the host program.

The files used for READ and WRITE are simple binary images. This can be created directly
by [asm85](http://github.com/TomNisbet/asm85) or can be converted from S-record or Intel
HEX using an external utility.

## Troubleshooting
* Verify that the Arduino type you are using is a supported board or that its I/O port definitions match one of the supported boards.  Some other Arduino boards, like the
Duemilanove, appear to be compatible but have not been tested. Others, like the Micro,
have different port mappings and definitely will not work without software changes.
* If the code doesn't appear to be working, concentrate on the read operations first to
verify that the data and address paths are good.
* 28C series EEPROMS, like the X28C256, sometimes ship from the factory with Data
Protection enabled.  Use the UNLOCK command to disable this. See the
[28C256 Notes](28C256-notes) for more information.
* Re-check all hardware connections and verify the the control pins are going to the
Arduino pins that match the definitions in the code.
* This repo contains a standalone program called HardwareVerify that allows low-level
access to the address, data, and control lines through a menu-driven interface.  See the [troubleshooting](troubleshooting) section for more tips.

## Further Work
* [ ]Add a new PromDevice class for 27 series EPROMS.
* [x] Additional error checking in the CmdLine code.
