PCF 8563 RTC Interfacing problem

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Hi friends,

I have interfaced pcf8563 chip with atmega32.
When the board is powered up, I am getting correct date, time information.
I am using code vision avr cross compiler.
1. I have set date and time using
rtc_set_date(...), rtc_set_time(...) functions

2. to read date & time, I using rtc_get_date(..), rtc_get_time(...) functions

I have used the rtc backup battery (CR2032).Connected to the circuit using two 1N4148 diodes.
To check the rtc is working on battery backup or not:

1. I have set date and time using
rtc_set_date(...), rtc_set_time(...) functions

2. I download the .hex file

3. then I have commented the rtc date, time setting part
4. after that I have downloaded new .hex file

I've verified the hardware connection, they seem to be correct.

problem:

When the system supply is switched off, I am not getting the updated date, time information( instead I am getting garbage values)?

1. Why the rtc chip is not working on backup battery?

Thanks in Advance.

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I your whole circuit running on the Cr2032?
If so then the voltage is to low. Battery voltage - voltage drop across the diode = 3V - 0.6V = 2.4V.

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Dear Vu_adam,

I am using seperate 3.3v supply for the rest of the circ uit.
The CR2032 is specifically used for rtc chip only.

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Read the PCF8563 data sheet. This shows the correct wiring for your battery. It also explains how it chooses the Vcc or the Vbat for supplying the chip. In a 5V system, if the Vcc is greater than a threshold it uses the Vcc.

David.