Reading, writing, erasing flash (16F88)

[RussMartin]

I'm taking trepidant steps toward using superfluous flash memory for recording data by implementing ERASECODE, WRITECODE, and READCODE.

I'm shuffling back and forth between the PBP manual and the 'F88 data sheet (sections 3.5-3.7) and I'm befuddled.


1. When a block of 32 words is erased, what value is written to each word to represent erasure? $3FFF. $0000? Something else?

2. Since (according to the data sheet) the write function writes a block of 4 words at a time, when the PBP command

WRITECODE Address, Value

is used, if Value is written into Address+0, what is written into addresses Address+1, Address+2, and Address+3?

3. Is the "erase before write" mandatory or simply advisory, and, if truly required,

4. How does the write function determine whether the address location has been erased?

5. And what happens if WRITECODE is invoked without a prior erasure?


What I'm trying to get a feel for, in advance, is:


A. As needed, can I simply do a WRITECODE to Address and then, next time, do a WRITECODE to Address+1 or will I need to

B. WRITECODE to Address, then, when needed, have to do an ERASECODE Address+1 and then WRITECODE Address+1? And

C. Having written a few or several values, is there a value I can look for that shows where I stopped writing (hence question 1 above)?