Electrical – DS2431+ EEPROM Toner cartridge Information

What you've been told about EEPROM's is ancient history. Modern EEPROM's are readily programmable in-circuit. You should read some datasheets of "typical" EEPROM IC's in order to understand how to use them; if you have any detailed questions, you can ask them here (in a new question).

The easiest way to find examples of EEPROM IC's is to search the websites of some of the major electronics vendors; the three that spring to my mind are Element14, Digikey and Mouser, but there are others as well.

There are two types, serial and parallel. Serial use 2-4 wires to signal data serially. Parallel use 8-16 wires for data, up to 20-odd wires for address and 3 or so for control.

Within the serial options, there are SPI and I2C. Given that you're using hardwired logic, I'd very much avoid I2C. SPI would be manageable though.

EEPROM datasheets generally give a thorough explanation of the low-level protocol required to read and write them.

My advice off the top of my head is that a something like a 25LC040 SPI EEPROM would be feasible.

We use the 9346 on several of our products, and it has this same dummy "0" devil thing.

I think the reason it does this is that it needs to have the last address bit (A0) clocked in before it reads the data and begins to clock out the requested data. If you look at the datasheet, You can see that the Dummy bit overlaps the A0 address bit.

You can fix this by fighting fire with fire :-). Add your own dummy devil bit to the end of the address word (Make the Length one longer), so that your SPI port ignores that first bit of the response, and begins clocking the response at the correct boundary.

Also, I always need to look closely to see that my CPOL and CPHA settings are correct. Sometimes things almost work when these settings are wrong, but are off by one bit (wrong CPHA), or sometimes just unreliable (wrong CPOL).