Chris, A PIC requires 4 clock cycles per instruction which limits the maximum output rate a PIC can provide as partial instruction times can't be used. With a 10 MHz input each instruction takes 400ns and if duty cycle isn't an issue nop instructions can be added each loop to extend the cycle period giving the following maximum PIC output rates with a 10 MHz clock.
2 instructions 1.25 MHz 50% duty cycle 3 instructions 833.333 KHz 33% duty cycle 4 instructions 625 KHz 25% duty cycle 5 instructions 500 KHz 20% duty cycle While a PIC can produce almost any division ratio for slower output rates the 4 clocks per instruction time limits the maximum rate a PIC can produce and generating a 1 MHz output with a 10 MHz clock is not an option. Richard > John, > > That's interesting to me. What exactly are the actual structural limitations > of > [that] pic? > > -CH > > On Jul 24, 2012, at 7:55, John Ackermann N8UR <j...@febo.com> wrote: > >> Unfortunately, the TAPR T2-Mini divider >> (http://www.tapr.org/kits_t2-mini.html) >> can't quite get to 1 MHz from 10 MHz with the PIC divider chip due to >> limitations >> in the chip architecture. >> >> However, nothing says you couldn't "dead bug" in a decade divider chip in >> place >> of the PIC, and let the T2-Mini provide the input conditioning, output >> driver, >> voltage regulation, connectorization, etc. for you, making it much a smaller >> project. >> >> John >> ---- >> >> On 7/24/2012 8:18 AM, Chris Wilson wrote: >>> >>> >>> 24/07/2012 13:14 >>> >>> My Racal Dana 9908 can take a 1 Mhz external reference. Inputting my >>> Thunderbolt at 10 MHz works, but shifts the decimal point over. I am >>> not sure if this has any other detrimental effects as to accuracy or >>> other? What's the easiest way to have a 1 MHz reference from the >>> Thunderbolt for this timer / counter please, yet retaining 10 Mhz for >>> my other devices that want a 10MHz reference signal? Thanks. >>> >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.