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'Detecting which device is in a programmer.'
2005\07\06@160411 by Peter Onion

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I've been looking at the code used by a couple of programmers to detect
the type of PIC that is in the programmer (or on the end of an ICSP
lead).

The general technique seems to be

1) Assume its a 14 bit core and try to read the ID word.
2) If ID word is valid return identified type
3) Assume its a 16 bit core and try to read the ID word.
4) If ID word is valid return identified type
5) return error.

I'm wondering what happens when there is a 16 bit core device in the
programmer, and the programmer tries to talk to it as if it was a 14 bit
core device ?

As far as I can see the risk of an unintentional "table write"
instruction being executed is very low as the 4 bit commands (18F) for
these are "11XX" and none of the 6 bit commands (16F) have the first two
bits as "1" as long as you send "0"s for all "don't care" bits.

Have I missed anything ?

Peter    



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