This sounds way to simple to be of use, but.... Just have the first minute after every even hour (except midnight) consist of 59 seconds. After all, as we have just seen, even god has to have "leap seconds" every so often. Bill ----- Original Message ----- From: "Jinx" To: "Microcontroller discussion list - Public." Sent: Wednesday, January 04, 2006 5:08 AM Subject: Re: [PIC] Fine-tuning oscillator >> I think the one on the oscillator input pin (can't remember off the >> top of my head whether that's OSC1 or OSC2) > > OSC1 > >> But why do you want to do this? >> Why not just buy a more accurate crystal > > I bought a load of 19.660800MHz for a product in which a small > deviation wouldn't be noticeable. Basically it has several modes, > from minutes measured in 100ths/sec or 10ths/sec to a few hours > in Hh:Mm or Mm:Ss. The customer has asked for a reasonably > stable time-of-day function to be added, which is no great bother, > except the crystals are around 130ppm fast (~19.663400MHz) > which will make a TOD about 11s fast per day. If I can get that > down to under 20ppm (say 1s/day or better) at an average ambient > (in this country probably 15C-20C) that would make me happy. > Or at least I could say I tried > >> then hoping that nothing else changes, like the temperature or the >> age of the crystal ? > > I think it's a pretty safe bet the crystal will age > >> You can get crystals down to 20ppm or so > > That's true. I didn't expect these to be quite so off. Others I've > had for timepieces (usually 3.2768MHz) have been pretty good, > but I need the 19.6608 for this. I can replace one of the SMT > caps with a trimmer quite painlessly. There's no need in this > product for a TXCO, and I do know what a trial they can be to > set up > > Although, had a TOD been required at the start I would have > made other arrangements for that part of it to be accurate > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist