What is your required output format? (SPI, I2C, ???) I figure you could do it with a small PIC and a 32KHz crystal using software CAL. I don't imagine you could manage anything much cheaper. Bob Ammerman ----- Original Message ----- From: To: Sent: Friday, March 26, 2004 4:00 AM Subject: Re: [EE]: Elapsed time counters (with calibration) ? > Hi, > > The thought had crossed my mind but this needs to be as 'cheap as [potato] > chips'. (<$1) > > One device that looked promising was the Dallas DS1318 but it is parallel > and has, oddly, no crystal calibration capability (considering the > accuracy provided by the subseconds counter). The requirement is for a rtc > with accuracy better than 5ppm @ 25deg C so there are two choices: > > a. Better than 5ppm xtal. > b. RTC with cal option + any cheap crystal. > > Currently, I use xtals that are about 20ppm (and use software cal) but > haven't had any information back regarding the cost differential between > the <5ppm and 20ppm xtals - do you think the cost would be prohibitive? > > Regards, > Dan > > > > A PIC? > > Bob Ammerman > RAm Systems > > ----- Original Message ----- > From: > To: > Sent: Thursday, March 25, 2004 6:08 AM > Subject: [EE]: Elapsed time counters (with calibration) ? > > > > Hi, > > > > I've been looking around for a 32-bit time counter (to replace a BCD > real > > time clock), possibly with sub-second resolution and found some Maxim > > parts that do the job but, unfortunately, do not have any 'internal > > calibration' functionality. > > > > Other RTCs I have used have had a 512Hz output which is used to program > > the internal register to compensate for using a cheaper crystal but I > > cannot any 32-bit counter with such a feature. > > > > Anyone know of a suitable part? > > > > Regards, > > Dan > > -- > 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