On Tue, 19 Nov 2002, William Chops Westfield wrote:

*>On that topic, does anyone care to describe techniques they use to get more
*>than one try out of an OTP device?  Seems like both all-zeros and all-ones
*>are reasonable harmless instructions to have happen before you start trying
*>to do real work so you ought to be able to put your program as high as
*>possible in program memory (so it occupies the top 100 words or so.)  Then
*>when the PIC resets it starts at 0, executes (memsize-100) NOP or ADDLW 0xFF
*>instructions, and then starts your program proper.  If it doesn't work, you
*>program your next 100 word program starting at memsize-200 and try again.

Yes, but if you do this often buy a 12C509JW.

*>(obviously, this doesn't work as well if you start needing interrupt vectors
*>and so on, but hopefully by the time your program gets that complex you've
*>got more experience and more flash alternatives.  It's the really "trivial"
*>first time attempts and such that I want to address.)

There are NO interrupt vectors to care for. There is OSCCAL so the first
instruction is MOVLW OSCCAL but the rest is as you described.

*>There may be difficulties with programmers and verifies and such, which is
*>why I'm asking for actual experiences...

Exactly. Open sourced programmers do not have this problem ;-). Also those
written specifically to cope with this kind of problem. Like the one I
wrote for our use for example.

Peter

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