LPC1769 internal RTC is not working properly

[lpcware]

Content originally posted in LPCWare by Dhananjayan on Fri Nov 23 05:10:39 MST 2012
I am using LPC1769 microprocessor. I have set all the registers correctly and connected capacitor and crystal across the oscillator terminals.I have observed that RTC is working fine, RTC_OSCF bit is cleared (Bit 4) in RTC auxiliary control register and the seconds value is incrementing every second.

But after finishing the test and starting the test next day this flag seems to be set and does not clears after clearing the bit by writing one to clear the flag. Also seconds value does not incrementing.

I removed the capacitor and reconnected it. Now i found the RTC_OSCF bit is cleared and RTC is working fine.

This happens again and again when i started doing the RTC test.

I have connected ABS25 crystal oscillator (32.786KHz) to the internal oscillator pin RTCX1 and RTCX2.

I have used 22pF Capacitor across the terminals of oscillator.

Please suggest me some ideas to overcome this problem.

[lpcware]

Content originally posted in LPCWare by riscy00 on Sun Mar 23 03:51:09 MST 2014
Suggest to use XOSC than XTAL......

[lpcware]

Content originally posted in LPCWare by probatista on Thu Mar 20 07:31:07 MST 2014
Hi,

Daniel, this issue only affects Rev '-' of this MCU, but not Rev 'A', right? That's what in Table 2 of the errata issue RTC.1.

In the errata there's no description of the effect of this issue, so in fact it is as you wrote? (RTC stops when temperature is high, works again when it lowers).

Regards,
Paulo Batista

[lpcware]

Content originally posted in LPCWare by Daniel Widyanto on Wed Dec 19 00:22:18 MST 2012
Hi,

The Rev-'A' of this MCU (LPC176x) has issue with the RTC. It will suddenly stop when the temperature rises, and running again  when the temperature is lower. Please refer to the errata (http://www.nxp.com/documents/errata_sheet/ES_LPC176X.pdf).

No fix for this issue, except updating the MCU revision to the latest revision.

[lpcware]

Content originally posted in LPCWare by hparracho on Thu Dec 13 07:47:46 MST 2012
Can we see the fragment of the source code in question?

Edit: You mentioned a test done in the next day... is the RTC powered for sure during this period?

[lpcware]

Content originally posted in LPCWare by Dhananjayan on Thu Dec 13 01:20:52 MST 2012
Help me Please