Re: MPC555 RTC Question

Hi David,

My RTC init routine:
 - unlocks RTCSC
 - sets RTCSC=0
 - sets 4M=1, SIE=1, RTF=1, RTE=1
 - sets the RTCIRQ

I do not enable alarm interrupts by setting the ALE flag, so I don't
think the value of RTCAL should have any bearing.

I've tried clearing any "pending" interrupt by writing SEC=1 before
enabling SIE=1, but the results were the same. 

--- In [email protected], David Wybo <realtimeconsultants@c...>
wrote:
>
> The USIU manual states:
> 
> The RTCAL is a 32-bit read/write register. When the value of the RTC is 
> equal to the
> value programmed in the alarm register, a maskable interrupt is
generated.
> 
> What do you initialize it to? Also, do you clear SEC before enabling
the 
> RTC?
> 
> trailrunner23 wrote:
> 
> >Wondering if anyone can explain something a little odd about the RTC.
> >I've got the RTC and PIT initialized to generate interrupts once per
> >second, and the DEC to generate interrupts once per millisecond. The
> >first RTC interrupt occurs as soon as I enable interrupts, but the
> >first PIT interrupt occurs very close to one second later. It doesn't
> >help if I explicitly acknowledge a (possibly pending) RTC interrupt
> >before enabling the interrupt. Anybody understand this? I want to
> >think of the RTC as the number of seconds that have elapsed since
> >boot, but it's always ahead by one second.
> >
> >Thanks,
> >
> >Joe
> >
> >
> >
> >
> >
> >
> >-----------------------------------------------------------
> >To learn more about Freescale Microcontrollers, please visit
> >http://www.freescale.com/mcu
> >
> >
> > 
> >Yahoo! Groups Links
> >
> >
> >
> > 
> >
> >
> >
> >
> >  
> >
> 
> -- 
> David Wybo                    mailto:david.wybo@r...
> RealTime Consultants, Inc.    Phone: 248.345.6160
> www.realtimeconsultantsinc.com
>






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