28C256 EEPROM Writer

This is a simple homemade EEPROM writer that any one can make.

To make a writer It requires the following

  • Breadboard w/jumpers

  • 2 - MCP23S17 16-bit SPI I/O Expander

  • Raspberry PI

*note the project is 100% directed towards the 28c256 EEPROM's. but you should be able to adapt the concept to other sizes of EEPROM's

Schematics

Python code

32k.zip 21 Jul 21

To run go to the command terminal in the folder with the files and type python3 32k.py

Includes

  • 32k.py

  • SPI32k.py

  • unlock_code.asm (this is for unlocking 28c256 on my 8088 motherboard see attached video)

32k ROM Unlock Code 8088 assembly

ORG 0X0000


;Setup 8255

MOV AL, 0X80 ;MODE 2 PORT B OUTPUT

OUT 0X63, AL ;WRITE TO 8255 COMMAND PORT

MOV AL, 0XAA ;WRITES 0XAA TO PORT 0X60

OUT 0X60, AL ;


MOV AX, 0XF000 ;SET UP DATA SEGMENT

MOV DS, AX ;

MOV BYTE [0X5555], 0XAA ;UNLOCK BYTES

MOV BYTE [0X2AAA], 0X55 ;

MOV BYTE [0X5555], 0X80 ;

MOV BYTE [0X5555], 0XAA ;

MOV BYTE [0X2AAA], 0X55 ;

MOV BYTE [0X5555], 0X20 ;


MOV BYTE [0X7FF0], 0X20 ;LEAVES A MARKER IN THE END OF THE ROM


HLT