Cannot exit StandbyMode on RTC alarm

[tj2]

Posted on March 27, 2008 at 06:41

Cannot exit StandbyMode on RTC alarm

[tj2]

Posted on October 24, 2005 at 07:21

Hi.

I cannot get our target board to wakeup from the RTC alarm. The code is working on the MB393B demoboard. So I think it's hardware related. But I cannot determine where the problem could be. I've verified the 32KHz clock and it is running...

[ben2]

Posted on October 24, 2005 at 07:29

is you main oscillator running ? To exit from any mode apart from wfi and lpwfi the main oscillator must be running

[tj2]

Posted on October 24, 2005 at 07:30

Yes, the main oscillator is running.

[tj2]

Posted on October 24, 2005 at 10:58

On the MB393B board J3 is fitted.

On our board a 1µF ceramic capacitor is connected between V18BKP (pin 55) and VSSBKP. VSSBKP is connected to GND. And there is not an external power source is connected to the V18BKP pin.

[tj2]

Posted on October 25, 2005 at 07:41

I've measured the voltage on the V18BPK pin and it was only 1.56V. Is this voltage too low for the RTC to operate?

[tj2]

Posted on October 25, 2005 at 07:56

The voltage on the V18pin is 1.85V when not in standby, and drops to the 1.56V when entering standby mode.

[tj2]

Posted on October 25, 2005 at 09:12

The Standby pin does not go high. There is a 100k pull-up connected to the pin.

When using the wake up pin the wake-up function correctly.

[tj2]

Posted on October 25, 2005 at 09:19

I've just changed PCU_LPMEnter ( PCU_STANDBY ); to PCU_LPMEnter ( PCU_STOP );

And here the RTC wake up function correctly. So it is somehow related to the standby mode.....

[tj2]

Posted on October 25, 2005 at 10:55

I made another test:

I thought maybe the 32KHz crystal didnt function during standby mode, so I made a program where the RTC_CounterValue() is send to the PC trough the UART. And the result is that the RTC _is_ running during standby. So I cannot understand why the alarm function wont work.