Siemens S5-100U User Manual page 310

The Integral Real-Time Clock
The following section is intended to help you to start running the integral real-time clock as quickly
as possible by setting parameters in the system data. You need to be familiar with the clock data
area described in sections 12.4 and 12.5 in order to understand this section.
Note
The clock time is updated one second after the start of the next cycle.
Task:
You want to set the clock to the following values:
Wednesday, 12.02.92; 10:30:00
The status word is assigned to flag word FW12. Clock data is stored in DB75 beginning with DW0.
The two ways to transfer clock settings are as follows:
• Use the STATUS VAR programmer function when the programmable controller is in the RUN
mode.
• Use the FORCE VAR programmer function when the programmable controller is in the STOP
mode and status word bit 4 = 1.
The following example uses the first method. Proceed as follows:
1. Set the programmable controller to Power OFF.
2. Set the operating mode switch to STOP.
3. Set the programmable controller to Power ON.
4. Perform an overall reset on the programmable controller. See section 4.1.3.
5. Use the following program to program the programmable controller.
6. Set the operating mode switch to RUN.
The integral real-time clock is running.
Program Structure:
OB21
FB1
OB22 FB1
FB1
12-16
The system data is defined during the change from
STOP to RUN.
The system data is defined when the programmable
controller is switched on.
Set the new date and time.
DB75
S5-100U
EWA 4NEB 812 6120-02