Forrest W Christian wrote:
> Well, I am working on a bootloader for the 18f46J11....
> 
> And came across this snipplet:
> 
> "To maintain the endurance of the program memory cells, each Flash byte 
> should not be programmed more than once between erase operations. Before 
> attempting to modify the contents of the target cell a second time, an 
> erase of the target page, or a bulk erase of the entire memory, must be 
> performed."
> 
> Add to that:  "The minimum erase block is 512 words or 1024 bytes."
> 
> This isn't a big problem for the bootloader (rewriting 1024K at a time 
> is ok - a bit dangerous in page 0, but not a big issue).    What is bad 
> is that this particular pic doesn't have any flash other than the 
> program memory, so I in effect get to use the program memory as flash 
> data memory to store my nonvolatile settings.
> 
> Assuming I am reading my datasheet correctly, that means I get to 
> reserve 1024 of the 3776 bytes of RAM so I can read the entire block of 
> configuration memory in, make modifications to it, and then re-write 
> it.   Am I missing something? 

Yes. You just have to reserve the same amount of RAM as you have
config memory/varabels in Flash. There is no reason to save/rewrite
flash that you don't use. You have to reserve the full Flash page
anyway of course, but you can rewrite the usused Flash area
with dummy data.



> 
> -forrest
> 
> 
> 
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