Integral Real-Time Clock (Only In The S5-95U); Function - Siemens SIMATIC S5-90U System Manual

S5-90U/S5-95U
13 Integral Real-Time Clock
13.1

Function

The integral real-time clock (hardware clock) offers the following possibilities of controlling the
process sequence.
• Clock and calendar function
used to configure clock-time dependent control, for example.
• Prompt and alarm function
used to monitor the duration of a process, for example.
• Operating hours counter
used to monitor inspection intervals, for example.
In order to be able to use the integral clock, you must assign the corresponding parameters in DB1
or program it in the control program.
Programming of the clock in the control program should be reserved to users with an extensive
system knowledge (see Section 13.6). All other users are recommended to assign the relevant
parameters of the clock in DB 1 (see Section 13.5).
The integral hardware clock requires a clock data area and a status word in order to function.The
following information must be stored in DB 1 or, when programming the clock in the control program,
in the system data 8 to 10 (see Appendix B):
• Location of the clock data area
• Location of the status word
Operating Principle
Data exchange between the integral real-time clock and the control program always goes through
the clock data area. The clock stores current values for time, date, and operating hours counter in
the clock data area. You can transfer into the clock data area the values for the time, date, prompt
time, and operating hours counter that you want the clock to use.
You can scan the status word to identify setting errors, for example. Or you can change certain
status word bits to deliberately disable or enable transfer or read operations.
The clock data area and the status word can have the following locations:
• Data block
• Flag area
• Input area
• Output area
Refer to Sections 13.2 and 13.3 for additional information about the clock data area and the status
word.
EWA 4NEB 812 6115-02b
Integral Real-Time Clock
(only in the S5-95U)
13-1