Hi Hal, I've reviewed this a bit and I used the wrong terminology. Either Timer1 or Timer3 can use the T1CKI input as a clock. Along with that, the CCP1 or CCP2 pin can be used to trigger a capture of the timer in use into the CCPR1 or CCPR2 register pair. I had considered this as an interrupt function, but after looking at the manual, it's a matter of switchable dedicated hardware. Sorry for the bad info.
Bob >________________________________ > From: Hal Murray <hmur...@megapathdsl.net> >To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency >measurement <time-nuts@febo.com> >Cc: hmur...@megapathdsl.net >Sent: Thursday, February 27, 2014 1:13 AM >Subject: Re: [time-nuts] GPSDO with all-digital phase/time measurement? > > > >b...@evoria.net said: >> At least on the PIC I'm using, the CCP and timer interrupts don't seem to be >> synchronous with the PIC clock. I could be mistaken. > >Unless you have a very strange architecture, it doesn't make sense for an >interrupt to not be synchronous with the CPU clock. You are in the middle of >an add instruction, and now you want to start an interrupt. What does that >mean? > >I expect there is the standard 2 FF synchronizer on all the input pins. >Things like the counter/timers run on the CPU clock, taking their input after >the synchronizer. I don't remember seeing a data sheet that comes out and >says that, but sometimes you can get some (strong?) hints with things like >minimum pulse widths or max clock rate. > > >-- >These are my opinions. I hate spam. > > > > > > _______________________________________________ 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.