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?
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
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 ;-)
chris
