> Swapped 32.768 khz crystal/caps for a 1.544 MHz external oscillator, into
> an 16F872 circuit.  This is an ECS-200 series oscillator in a 14-pin metal
> pkg, but only has 4 pins, and only 3 of those are active -- +ve, gnd, and
> out
> (which I connected to OSC1/CLKIN).  OSC2/CLKOUT is now open.
>
> Pre-scaler is now 1:8 and ISR routine divides a few times:  first by 193,
> then by 25, then by 10, to give me 1-sec pulses.  (There's a reason for
> those divisors in case you're wondering -- I can get 0.1 sec pulses I need
> for something else).
>
> However, it's running MUCH slower than that -- taking a few minutes to
> generate a 1-sec pulse!

Watchdog issues?  Does the algorithm do what you expect when you emulate or
simulate it?

> Am I missing something here?  I've left the osc config bits to LP,

You should be using XT at 1.5MHz.

> and
> verified the ext osc freq with an oscilloscope.  Also, there's a setting
in
> OPTION_REG for selecting the source clock for TMR0 to internal or
> T0CKI, but I don't think this setting has anything to do with this prob.

That depends on whether you are using timer 0 in your divider chain.  Also
note that when the timers are driven internally, they are driven from the
instruction clock, not the oscillator frequency.  The instruction clock is
the oscillator/4.


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