A simple EEPROM programmer for 28CXXX devices, based on the Adafruit FT232H breakout. This has been hacked together to work with AT28C256 chips but could be adapted to similar devices. Based on heavily on the EEPROM programmer used in Ben Eater’s 8-bit CPU project.
__________ __________
| ft232h | | 28c256 |
| | | |
| d0 |----------------------------| d0 |
| d1 |----------------------------| d1 |
| d2 |----------------------------| d2 |
| d3 |----------------------------| d3 |
| d4 |----------------------------| d4 |
| d5 |----------------------------| d5 |
| d6 |----------------------------| d6 |
| d7 |----------------------------| d7 |
| | | |
| c0 |------+ ____________ | |
| c1 |----+ | | 74hc595 | | |
| c2 |--+ | | | | | |
| | | | +-----| srclk qa | | a15 |
| | | +-|-----| ser qb |----| a14 |
| | +-|-|-----| rclk qc |----| a13 |
| | | | | | qd |----| a12 |
| | | | | | qe |----| a11 |
| | | | | | qf |----| a10 |
| | | | | | qg |----| a9 |
| | | | | | qh |----| a8 |
| | | | | | | | |
| | | | | | qh'|-+ | |
| | | | | |__________| | | |
| | | | | +--------------+ | |
| | | | | | ____________ | |
| | | | | | | 74hc595 | | |
| | | | | | | | | |
| | | | +---|-| srclk qa |----| a7 |
| | | +-----|-| rclk qb |----| a6 |
| | +-------+-| ser qc |----| a5 |
| | | qd |----| a4 |
| | | qe |----| a3 |
| | | qf |----| a2 |
| | | qg |----| a1 |
| | | qh |----| a0 |
| | |__________| | |
| | | |
| c3 |----------------------------| /ce |
| c4 |----------------------------| /oe |
| c5 |----------------------------| /we |
|________| |________|
Pins d0-d7 on the FT232H drive the EEPROM data lines, while c0-c5 act as control pins. c0, c1, and c2 drive the shift registers to the device address. c3, c4, and c5 drive the various enable pins on the EEPROM.
On the shift registers, the /srclr pin should be tied high.
Usage ft232h-eeprom -r <file> -w <file>
-r <file>: Read eeprom contents to file
-w <file>: Write file contents to eeprom