I've had quite a bit of experience with 16F series PICs but am just getting 
started with 18F series PICs.  In the datasheet for the 18F252 I found the 
following language:

==================snip===========
For this reason, variables that change infrequently (such as constants, 
IDs, calibration, etc.) should be stored in FLASH  program memory.

Note: If data EEPROM is only used to store constants and/or data that 
changes rarely, an array refresh is likely not required.

===================snip==============

This seems to me to be a contradiction.  In the first section it says that 
EEPROM is to be used for values that change frequently and that flash 
program memory should be used for values that don't change frequently.  In 
the second section it seems to be saying that it is just fine to store 
constants and values that change infrequently in data EEPROM.  Does anybody 
know which of these is correct?

Elsewhere the data sheet says that EEPROM retention is 40 years or 
better.  Then there is that rather peculiar specification D124 that says 
that you need to perform a refresh every 1 to 10 million Erase/Write 
cycles.  But wouldn't an Erase/Write cycle constitute a refresh?  And why 
refresh every 1 to 10 million Erase/Write cycles when according to the 
datasheet the part is only rated for 1 million write cycles?

Can anyone shed any light on this?

Thanks,

John Hansen.

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