Set 24 / 12 hour and AM / PM of RTC

[PA3040]

Dear All,

My RTC DS1307 reading writing and adjustments are now working properly

The only thinks that I have to manage to set 24/12 hour and AM / PM accordingly

I mean after adjusted 24 / 12 hour and re writing to RTC not working properly

I know that bit 6 of address 0x02 of RTC should be 0 for 24 hour and 1 for 12 hour

Please advice with the logic that I have to consider in simple code

My MCU 18f452
Compiler HI TECH C lite

Please advice

 

[jayanth.devarayanadurga]

What values are you writing to hour register and for what format, 12 hr or 24 hr?

In 24 hr mode...

0x22 gives 22 hr

0x23 gives 23 hr

0x02 gives 2 hr

 

[PA3040]

In the 12 hour mode

0x51 11 AM

When I set the above value to hour register and compile the source code and program to the PIC then it is working well

But after resetting time then the new saving will effect the problem ( Adjusted time using micro switch )

please advice

 

[jayanth.devarayanadurga]

For resetting. You have to stop the clock and then write the new RTC values and then start the clock.

 

[PA3040]

I think you think
I2CSend(0x80); //write $80 to REG0. (pause counter + 0 sec)

I did it

 

[jayanth.devarayanadurga]

Post your circuit. Does your RTC has a 3V battery?

 

[PA3040]

Post your circuit. Does your RTC has a 3V battery?

No,I do not have installed the 3v battery

- - - Updated - - -

I am really asking, after resetting the time
how we set the new value for hour register without effect to the bit 6

is it necessary to OR or AND operation , then how and nay example

 

[jayanth.devarayanadurga]

If you want clear a particular bit then you AND that bit with 0 and if you want to retain the value of that bit then you AND with 1.

 

[PA3040]

Is this the only way to toggle between 24 and 12 hour mode ?

 

[jayanth.devarayanadurga]

Read the datasheet. The AM PM bit becomes 2nd 20 hour bit in 24 hr mode. So while toggling between modes you have to set the whole register. You can't modify just a single bit of any DS1307 register. You have to write the whole register with a new value.

 

[PA3040]

Is this correct?
1. After adjust
2.convert to BCD
3.write to new value to RTC

But in the hour
First adjust the hour
Convert to binary
AND operation with expected mode ( 24 or 12 )
then convert to the BCD
Then write to RTC

Is this correct?