Not enough EEPROM

[ljbeng]

I am using the 18f452 and I need 350 bytes of non-volatile memory. The EEPROM is only 256 bytes. Is it wise to use the program flash space for memory back-up. Is there a CCS example that shows the best way to do this? Thanks.

[Ttelmah]

Depends how often you want to change the memory contents. The EEPROM, typically has at least ten times the read/write 'life' of the main memory, and in some chips hundreds of times the life. Really much easier/safer to just add an external memory, if the values have to change at all often. If instead of EEPROM, you use FRAM, you get faster write access, and much larger sizes.

Best Wishes

[PCM programmer]

[valemike]

The PIC18F4525, which is a pin-to-pin replacement, has 1024 bytes of eeprom. Consider the upgrade.

[future]

[valemike]

I'm not sure.

You have to re-map any registers according to the datasheet. In general, some devices have extra modules (e.g. comparators) whose power-up default values has these modules enabled, and you have to explicitly undo these if you want to use them as digital i/o.

The quickest way to find out is to do your compile and run it. If certain I/O are not toggling as you want, then you might want to read in further about that specific i/o port. I usually just start off changing any register mapping, and compile as-is, then when all else fails, i read the manual.

Since you're migrating between 18F to another 18F device, it shouldn't be as tedious as migrating from a 16 to an 18.