DS1337 - 12h to 24h mode

[Tabsoft]

Reading the DS1337 Datasheet if bit 6 is High (1) 12hr mode is selected. See snippet from the Datasheet below.

"The DS1337 can be run in either 12-hour or 24-hour mode. Bit 6 of the hours register is defined as the 12- or 24-hour mode-select bit. When high, the 12-hour mode is selected."

With or without refers to the need, when in 12Hr mode, to mask off(set to 0) BOTH the 12/24Hr and AM/PM bits when using LCDOUT, SEROUT, HSEROUT, etc ; and when changing the value of the Hours in your code to be written back to the RTC. Such as when you allow the user to change the time via buttons.
With = Bits ARE NOT masked ( leads to errors)
Without = Bits ARE masked

Not performing these actions when needed during hour value manipulation and displaying the values will lead to incorrect settings in the RTC and visually strange clock display. E.g. 44 being displayed on the LCD instead of the expected 4 AM or 64 being displayed on the LCD instead of expected 4 PM.

[Tabsoft]

Just for grins, try doing 2 successive writes to the RTC with a 10ms pause in between.

I've ran into these kind of issues whenever the hours.6 bit is changed in the RTC.
Do this when you 1st initialize the RTC on startup and every time you write to the RTC.
The issue is when the 12/24hr mode bit is changed (hours.6).

From the DS
"All hours values, including the alarms, must be reinitialized whenever the 12/24-hour mode bit is changed."

[lerameur]

Hello,

I think I found the problem but I dont know how to get around it,
I have bit 5 confusing me when in 24H mode. How do you remove it from calculation,
The problem is this,
You need to get only number between 20 and 23H used with bit 5.
You also need to know what time you are now to do the calculation, at 18H hour you dont need it so RTCHour is 4 bits
at 20H you need the 5 bits,
So which and when to separate the two,... it seems to me like a chicken or egg issue.. which came first,, or in this case .. which to calculate first

[Tabsoft]

The only time you should need to worry about bit 5 is when bit 6 = 1 (12 hour mode).

When bit 6 = 0 (24 hour mode) you do not have to remove or mess with bit 5. Bit 5 is part of the number [B]not[B] an am/pm bit.

24Hr mode

Time is 11:00 hours, hours = %00010001 notice bit 5 is a zero which means the 2nd 10s is clear, and bit 4 (1st 10s) is a one which is set.
Time is 21:00 hours, hours = %00100001 notice bit 5 is a one which means the 2nd 10s is set, and bit 4 (1st 10s) is zero which is clear.

[Tabsoft]

Try removing or commenting out the following line from your ADDHour routine within the "if hourmode = 0" block (24 hour mode)
if BCDResult_temp > 12 then RTCHour.5 = 1

[lerameur]

Hi again,

here is you example with different hours..

24Hr mode

Time is 23:00 hours, hours = %00100110 notice bit 5 is a one
add 1 to 23
Time is 00:00 hours, hours = %00000000 notice bit 5 is zero
SO the bit 5 does changes int he 24H mode...
maybe i'm still not seeing it good..

[lerameur]

HooHoo ! , got it all working now.

Ya bit 5 was a bit confusing,
thanks a million for your time