![eeprom is write-protected eeprom is write-protected](https://i.stack.imgur.com/VvFrF.png)
I suspect a couple things: 1) The wiring. It start programming 0x54's alongside the 0x55's, and slowly the rest of the data pins fail, leaving the rest of the EEPROM programmed with all 0x00's. After some fiddling around with the order of the tests / disabling the SDP in your code, I actually managed to do it! I used your clearEEPROM function to write 0x55 to all addresses in the EEPROM, and it works for about the first 6000 addresses, then it looks like it start getting noise. I didn't know about the D13 controlling the onboard LED, so I changed it to an analog pin instead, and added some decoupling capacitors. I read your blog post, and we almost had the same pinout. The code also includes an updated routine to program the 7-segment display driver EEPROM so it blanks the leading zeros and moves the negative sign next to the numbers.Īll code should still work with the original programmer for writing 28C16 chips but the wiring will need to be updated to reroute the control signals for the EEPROM.īlog article describing the hardware changes and SDP code is at
![eeprom is write-protected eeprom is write-protected](http://j5d2v7d7.stackpathcdn.com/wp-content/uploads/pinouts/ST-Microelectronics/24C16.gif)
I've also modified the code to run a lot faster - I'm seeing the full 32Kb being written in about 15 seconds. So I updated my Ben Eater EEPROM programmer to use the 28C256 and wrote the code to disable SDP, or to write to the chip while SDP is enabled.
EEPROM IS WRITE PROTECTED HOW TO
There's a semi-regular theme on here of people buying a 28C256 EEPROM and finding out that the Software Data Protection is enabled and they can't work out how to disable it.