Oops -- looks like I accidentally erased part of my message...

Outside of all the WDT suggestions, what circuitry is he allowed to put o=
n?
I'm thinking that charging a capacitor and measuring with an a/d or
comparator input could also provide a fairly accurate pic-clock-independe=
nt
time reference w/o the resistor even.   Connect the cap to one of the dig=
ital=20
inputs which has the pull up resistor, and connect that input to an a/d i=
nput=20
as well.  Switch digital output to low, then switch to input and measure =
the=20
charge time.  Haven't actually done this though, but it sounds reasonable=
 in=20
my head. :-)

Cheers,
-Neil.


On Tuesday 06 May 2003 20:45, William Chops Westfield scribbled:
>     To rephrase it, he thinks that he can figure out, in software, the
> number of MIPS of the machine he is running on.
>
> You can come up with a "reasonable" guess as to clock speed on a PIC or
> related processor by seeing how many instructions it will execute in
> between watchdog timeouts (the WDT timer is normally a separate RC
> controlled clock, I believe.)  You could probably get a bit closer with
> a single resistor and cap connected to an IO pin, PERHAPS even using th=
e
> pin's inherent capacitance and leakage...
>
> It depends how accurate he needs to be, and whether he's allowed to mak=
e
> baseline measurements to compare to, and so on...
>
> BillW

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