I started working on a bootstrap for the PIC18F44J10, and was surprised 
to find that the size of a block erase is 1024 bytes.  The datasheet 
says that the block erase is required for at least every third write 
which makes me think I have to use it rather than writing a block of all 
FFFF to a 64 byte flash write block to do a pseudo erase.  The problem I 
have with that is that if I want to maintain memory on the part that is 
never erased, the size of that memory must be at least 1K.  So, if I 
want to have the boot block at the start of memory to encompass the 
reset and interrupt vectors, that's 1K of codespace that I can't erase 
at the start, and in addition, if I want to maintain the configuration 
bytes at the end of program memory, that's another 1K of code that I 
don't want to ever erase.  That leaves me with only 14K of usable code 
space for the part.  I can live with that for my current application, 
but it seems pretty wasteful.  Am I not thinking about this correctly?  
Will a 64 byte block write of all 1's effectively substitute for a cell 
erase?  I've looked at the App note 851, and although it claims to apply 
to all PIC18F devices, it was released in 2002, and refers to 
configuration bytes in different memory spaces so I don't think it 
covers this part.

Thanks,

Tony

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