Chris Liechti wrote: > > Garst R. Reese wrote: > > Hi folks, > > I'm running an msp430f149 with a 100kHz xtal (ECS=1.00-12.5-13) on the > > low frequency clock input. It seems to actually be running at 90kHz :( > > did you measure the clock output? (e.g. outpu ACLK), or doe you meausue > it with software? I calculated the time to fill a 64Mb MMC at 5.85h, but it actually took 6.5h. I also put a scope on pin that should trigger every 250us from TimerA, and it was a bit late. TimerA triggers a sequence of 6 AD conversions. > if you make an RTC with timer_a use e.g. > CCR1 += TA_ONESECOND; > and not > CCR1 = TAR + TA_ONESECOND; > > the later can run away if you dont service the interrupt within the same > timer tick... > > if its hardware.... > isnt the LFXT optimized for 32kHz crystals? > if so, then is the center frequency of the oscillator much lower than > your xtal and it tries to tie the frequency toward its center frequency
Yeah, I may have to go to a 32kHz xtal, but someone reported a 100kHz xtal working , so I think I will try another brand first. 100kHz gives me an even divider for 250us. > an other problem can be if the capacitors on the xtal pins dont match > the recomended values, see datasheet of your xtal. > > > A similar problem is showing up on the DS1305 RTC, which has a 32kHz > > crystal, but it too is running very slow, losing about an hour a day. > > Any of you hardware folks have an idea? > > well and there may be the relativity theory in play. but i doubt that > you move around your hardware in near light speed ;-) Not recently, but assuming I'm moving with it, I wouldn't see an affect. ;>) Thanks, Garst > chris > > ------------------------------------------------------- > The SF.Net email is sponsored by EclipseCon 2004 > Premiere Conference on Open Tools Development and Integration > See the breadth of Eclipse activity. February 3-5 in Anaheim, CA. > http://www.eclipsecon.org/osdn > _______________________________________________ > Mspgcc-users mailing list > Mspgcc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/mspgcc-users
