write_program_memory() for data storage PIC18Fxxxx?

[Ken Johnson]

Using a high-end 18Fxxxx (perhaps 8722), I need to store some user setup info, more than will fit in 1K EEPROM.

What are the pros/cons of putting it in some un-used program memory using read/write_program_memory()?

Thanks,
Ken'

[Ttelmah]

Number of cycles. The program memory has a much lower write life multiple than the EEPROM.
Block size. Normally the program memory has to be written in a block, not as a single byte (CCS has functions that hide this from you - write_program_eeprom - but remember if you use this, and change several bytes in one block, all the bytes have then had as many cycles, as write operations...).
Timings. With the EEPROM, other things can occur while the memory is written. With the program memory, the processor actually has to effectively stop during the write. This can interfere with things like serial communication etc..
If the data is likely to have to change at all frequently, consider just adding an external EEPROM.

Best Wishes

[newguy]

Someone on this forum has, for years, raved about Ramtron FRAM serial memories. I have recently started using them based on this person's positive reviews (sorry, can't remember who), and they are superb. They have an essentially unlimited lifetime and come in I2C or SPI interfaces. Great products, I highly recommend them.

[Ken Johnson]

Just read about the Ramtron FRAM - looks like the answer

Many thanks,
Ken