From my brief overview you are limited by no extra pins, and it uses an RC oscillator. Your options, to get 10%, is to replace the resister and capacitor with 1% or better parts (prefereably parts which are not affected by temperature by more than 1% for a total of 4% maximum out of range), or remove them entirely, cut the extra osc trace (if it goes anywhere) and add a surface mount resonator either directly to the traces (if space and layout permits) or with the adition of one or more wires and a dab of epoxy to fix it to the board. In order to get the software to detect whether it's in range or not you must have a steady reference to compare it to. There's nothing in the explanations you've made which could act as such a reference. Perhaps if you tell us what the PIC is connected to we could come up with a system in software. the PIC has nothing intrinsically which could act as a reference, but you might be surprised at what types of already attached hardware could be made into a reference. Lastly, can you calibrate them before putting them to use? If you calibrate each device before use so you know the temp coefficient of the RC oscillator and the temp coefficient of the WDT, you may be able to solve the three variable equation which would give you temperature and thus the speed of the RC oscillator. Chances are the curves will be quite close, though, so you may not be able to obtain any useful data, especially considereing that the RC and WDT could easily be at slightly different temperatures. -Adam Tony Pan wrote: >>Frankly, this whole thing sounds like a kludge to work around a bad >> >> >design. > >I agree. > > > >>What overall problem are you trying to solve? What tolerance do you need >> >> >to know your clock is within. > >I want to have an accurate timer. If it's not accurate I rather let the >operation discontinued. The tolerance is 10%. > > >----- Original Message ----- >From: "Olin Lathrop" >To: >Sent: Friday, September 13, 2002 7:52 AM >Subject: Re: [PIC]: Monitoring internal clock? > > > > >>>I will run the check at powerup, if the clock is off, I reset the >>> >>> >>processor. >> >> >>>If it keeps being off, it would always be reset. I don't need to correct >>> >>> >>the >> >> >>>frequency. I simply don't run the software if the clock is off. >>> >>>Is that possible? >>> >>> >>The firmware can not tell how fast it's own clock is running without some >>other timing reference. The watchdog timer runs from an independent >>internal R/C oscillator, and can therefore be used as a reference. Of >>course the accuracy of the answer is only as good as the accuracy of the >>reference. Other possible references include a separate timer 1 >> >> >oscillator, > > >>or an external R and C used as a single one-shot event timer. >> >>Frankly, this whole thing sounds like a kludge to work around a bad >> >> >design. > > >>What overall problem are you trying to solve? What tolerance do you need >> >> >to > > >>know your clock is within. >> >> >>***************************************************************** >>Embed Inc, embedded system specialists in Littleton Massachusetts >>(978) 742-9014, http://www.embedinc.com >> >>-- >>http://www.piclist.com hint: To leave the PICList >>mailto:piclist-unsubscribe-request@mitvma.mit.edu >> >> >> >> > >-- >http://www.piclist.com hint: To leave the PICList >mailto:piclist-unsubscribe-request@mitvma.mit.edu > > > > > > > -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu