> > But you don't need a RTC for that, just an accurate crystal.
> 
> Well, yes, but (not really wishing to split hairs) there is a distinction
> to be made between what an RTC is and what does it. For example
> an external device could be more efficient if keeping the PIC awake
> used more power. And typically bare crystals do drift. Many RTC
> ICs have TCXO, at a price sometimes


All the units I've got (various brands, all cheap ones) keep very good time.
I tend to carry one in my pocket instead of wearing a watch, a nerdy fob
watch if you will.

I'm guessing they've got the ubiquitous 32k watch crystal in them, I've
never opened one up to see.  More than enough to keep up with a 13Hz signal.
If you want a 1 second source the pulse generator out of a cheap clock will
do (they use a 32k crystal too).

The OP should do the display in binary or something.  Maybe PWM a panel
meter.

Tony

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