[SOLVED] LPC2138 rtc battery backup does not work correctly

[mi14chal]

I have a problem with an internal RTC in LPC2138 b/c battery backup does not work, when I unplug power supply and then plug it I get a random time it seems that battery backup does not work correctly but why? Here is a schematic of connection page 1: https://wydawnictwo.btc.pl/pdf/zl7arm.pdf and this code I'm using to configure RTC:

CCR = (1 << 0) | (1 << 4); // Clock enable and choose the external oscillator

 

[jayanth.devarayanadurga]

Which RTC is used in that module? Is it internal RTC of LPC micro?

 

[mi14chal]

As I said earlier I'm using an internal RTC in LPC2138.

 

[mi14chal]

I found out why it won't work. This module which I bought has connection between Vbat and Vdd... so a battery is not enough to power uC. I chose external RTC and now it works perfectly.