Post by thread:[PIC]: Long Accurate Timing loops

I've been away from PICs for some time now I've recently offered to write a program that involves frequency counting and so I got to thinking about timing loops. I searched PICLIST and it seemed as if there were long time delays, accurate time delays, but no long and accurate timing delays. I recall some discussion on this and a few one-byte counters that were cycle accurate. Would anyone like to comment on this code fragment for a two byte cycle-accurate delay loop: movlw high delay movwf delayhi movlw low delay movwf delaylo d1 incf delayhi,f movlw D'5' loop subwf delaylo,f skpc decfsz delayhi,f goto loop ;5 cycle loop comf delaylo,w addwf PCL,f nop nop nop nop d2 The delay between d1 and d2 is the value of "delay" plus nine cycles and I have been unable to find any trick values that trip it up so far. The loop finishes with a negative number in "delaylo" and COMF converts it to a number between 0 and 4 used to add up to four "noops" I guess that on a 14 bit pic delaylo could be stored in the W register? Oliver -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

Why not get the "Zero-Error One second timer" from Roman Black. Written in MPASM and available at http://www.romanblack.com/one_sec.htm This can modified for any time delay. Great bit of code. BTW, whatever happened to Roman ? Rgs Ian. > {Original Message removed}

Oliver Broad wrote: > > From: "Jan-Erik Soderholm XA (TN/PAC)" > > > Why not use one of the timers ? > > Jan-Erik. > > I'll be using the timer to count pulses! > *The* timer ? Most PIC has a couple of them, maybe use one timer for the "window" and another for the counting... Or is this a 16F84 design ? I think that one had just one timer (?)... Jan-Erik. -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestKILLspammitvma.mit.edu

On Mon, Nov 17, 2003 at 09:55:37AM +0100, Jan-Erik Soderholm XA (TN/PAC) wrote: > Or is this a 16F84 design ? I think that one had > just one timer (?)... No, two. TMR0 and the watchdog. The latter includes a potentially useful temperature dependency. -- James Cameron .....quozlKILLspam.....us.netrek.org http://quozl.netrek.org/ -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestspam_OUTTakeThisOuTmitvma.mit.edu