Thanks for the clarification. I only graduated in May though, so I didn't
make the mistake the first time! <G> I'll get it done right, thanks.
 James

 On 9/27/05, Olin Lathrop <olin_piclist@embedinc.com> wrote:
>
> James Humes wrote:
> > Are there any suggestions for fixing this in a way other than my
> > insertion of NOPs method?
>
> Yes. Your method got you into trouble because it tried to do a dumb edit
> on
> the HEX file instead of interpreting it properly, making modifications,
> then
> writing it back out. There are many legal ways the HEX file can be writte=
n
> that can be different at the low level syntax.
>
> Another point is that it would be best to put RETLW h'FF' in the source
> code
> with an appropriate comment what the value means and that it will be
> filled
> in during production test. That would also give you the option of
> modifying
> the value in place after the programming step in case that is more
> convenient. I use this method for a current customer. The firmware is
> first programmed into the device because it needs to run in order to
> collect
> the data for calibration. Once the data is collected, the FFh is
> overwritten with the computed value without reprogramming the device. You
> can always flip 1 bits to 0 but going the other way requires an erase
> operation, often on more than a single memory location. The source code
> specifies FFh because that is the erased state.
>
> If you can determine calibration values up front, then making a temporary
> custom HEX file will be the fastest way to get there since only a single
> programming operation is required. This should be done by actually readin=
g
> the HEX file properly according to the spec, changing selected values,
> then
> writing out a new HEX file with the custom values. If you don't properly
> read the HEX file, you'll probably have this problem again some time in
> the
> future even if you manage to kludge around it now.
>
> Reading a HEX file is easy. Doing it right in the first place would
> probably have taken less time that you already spent finding and thinking
> about this issue 7 years later. Don't make the same mistake again.
>
>
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