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
Resources:
The files can be found on GitHub
https://github.com/homebrew8088/Raspberry-Pi-32k-EEPROM-Programmer
Schematics
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