system clock in S5 115U with CPU 943

I read the system-time and date in a S5 115U (CPU 943-7UB21).
That works perfect.
Now I want to do the same in a CPU 943-7UA21 or a CPU 943-7UA22. Not good
I have looked in the manual, and there they say that the system clock only exists with cpu's with 2 serial interfaces. Well, there are 2 serial interfaces on my CPU's. What's the problem then?? DB1 ??

Hi Greet,

According to this the 943-A didn't have a real-time clock.


Kevin H

As Kevin states the A series doesnt have a clock

Thanks for the answer!

I want to log the time & date when an alarm comes up. Normally I put the time & date in a DB.
How can I solve this now, when I don't have a system clock?

Hi Greet,

As I see it you have 3 options...

1. Get a 'B' series CPU as a replacement.

2. Does the system have a HMI? On S5 systems in the past, I have used the real-time clock from a Lauer PCS series HMI for similar timestamping functions. (they map the RTC to the interface DB)

3. Program your own clock/calendar. It won't be very accurate as it stands so it's a good idea to use an external real-time clock wired to an input to synchronise your's on a daily basis. Tip: don't synch at midnight as it could affect your day rollover.

Kevin H