CCS/BQ32000: OF bit can not be cleared after manually stop and start the RTC

Hi Daniel,

I am not sure I understood the last part of your statement.  Perhaps a sequence will help:

Step	STOP State	OF State
1 (Power on)	0	1(default)
2 Write OF = 0	0	0(write)
3 Oscillator normal run	0	0
4 Stop oscillator	1 (write)	0
5 Read during osc stop	1	1 (OF flag set)
6 Restart oscillator	0	1
7 Clear OF flag (must write 0x1.7 = 0)	0	0 (write)
8 Read minutes	0	1

You are saying that with the above method, the OF flag does not stay cleared after step 7, but keeps getting set to 1?  Are you changing the other bits of register 1?  Are you writing multiple bytes in a single I2C transaction?

Best Regards,

Hi Rob,

   Yes, the sequence you listed is just the same as what i have done.  Under normal running state, after stop the OSC(STOP bit), the OF bit will be set but can not be cleared  after  restart the OSC(STOP bit) . I have try to use both  multiple bytes write (sync time from SECOND to YEAR) and  single write(MINUTE register) to clear OF bit,  both failed.  However, if i remove both main and backup power of BQ32K for a while. Then recover the backup and main power, then i can clear the OF bit from I2C bus.

   For the OF bit change from 0 to 1, it takes several clocks after OSC is stopped.  

  For I2C bus operation, i have checked the signal with logic analyzer. All read and write operations are OK.

Hello Daniel,

I apologize for the delay, is there any update on your situation?

73,
Timothy

Hi Timothy,

   There is no update on the event. The issue is  still open.

  

Hi Daniel,

I want to verify that you are writing 0 to the OF flag after the oscillator is stable.

It appears similar to the thread here: e2e.ti.com/.../627668

If you are writing 0 to the OF flag. Have you written multiple times?

If still not clearing, have you tested with other devices/boards? Is this on a custom board, or are you using the EVM?

Best Regards,

Hi Rob,

  Yes, I am writing 0 to OF flag and have written multiple times after the oscillator is table. The operation is done on my custom board and i do not have the EVM on hand. 

Hi Daniel,

This is unusual behavior. My apologies for your troubles.

I believe that there may be some problem with either the oscillator operation, or the device. if you have multiple boards, checking others may be helpful.

If you can also provide a schematic, I'd like to review the oscillator portion.

I have not found any device history on not being able to clear the OF flag.

Best Regards,

Hi Rob,

    Yes, we do have multiple boards because it's under pre-production state. We temporarily disable the STOP oscillator feature because it's low power consumption even keeping running.

  Here is the schematic of RTC part,

    

Can help check if anything wrong from the design ?  Thanks for your support.

 

Hi Daniel,

I don't see an issue with your schematic.  I am trying to get access to more internal documentation to help you and I am having a difficult time.  I will have an update for you by the middle of next week.

Best Regards,