Siemens SIMATIC S5-100U, System Manual

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S5-100U The Integral Real-Time Clock
Storing the Updated Time/Date after a RUN to STOP Switch
Note
This clock data area is only written to if the following requirements are met.
• Bit 5 in the status word is set to “1”.
• A RUN to STOP switch or a Power OFF has taken place.
• The necessary memory space is available in the operand area.
This enables you to detect a RUN to STOP switch or a Power OFF even if the programmable
controller has since gone back to RUN mode. The time and date of the last RUN to STOP switch or
Power OFF are in words 18 to 21 (see Table 12-3)
If several RUN to STOP switches have occurred before you read out this clock data area, you will
only be able to determine the time of the last switch.
If you do not have sufficient memory for this clock data area, you either cannot use this area or use
only part of it. This has no impact on anything else.
12.7.2 Programming the Prompt Function
Transferring Settings to the Clock
• You can store the settings in the clock data area by using transfer operations (see Table 12-3).
• The AM/PM flag (bit number 7) is only significant in 12-hour mode.
Bit 7=1 means PM
Bit 7=0 means AM
• You must transfer the clock data in BCD code.
TIP: The “KC” data format loads a BCD constant into ACCU 1 and is therefore especially
suitable.
• If you enter the value “255
D
” or “FF
H
” in a byte as the prompt time, this byte will be ignored
when evaluating “Prompt time reached”. This makes it easy to program, for example, an alarm
that is repeated daily by entering the value in the “255
D
” or “FF
H
”in the “Weekday”, “Date”
and “Month” settings.
• You can transfer the prompt time settings to the clock by initiating bit 14 in the status word.
• The settings are transferred 1 second after the start of the next cycle.
• Bit 12 in the status word displays incorrect settings.
EWA 4NEB 812 6120-02b
12-25