Siemens SIMATIC S5-100U System Manual page 314

The Integral Real-Time Clock
Operating Hours Counter Flags
Table 12-7. Significance of the Operating Hours Counter Flags Bits 8, 9, and 10 of the
Status Word
Bit Number Signal State
8
9
10
Prompt Time Flags
Table 12-8. Significance of the Prompt Time Flag Bits 12, 13, and 14 of the Status Word
Bit Number Signal State
12
13
14
The operating system requires bit numbers 6, 7, 11, and 15. You can not use these bits.
Scanning the Status Word
In a data block, you can use the "P <data word number> <bit number>" operation to scan the
individual bits of a data word. In the flag area, you can scan the individual bits if you enter the
<byte address> and the <bit number>.
Example: The status word is stored in DW13. You are checking to see if the set prompt time has
been reached. The "P D 13.13" instruction triggers a scan. If the status word is stored
in FW12, then the same scan would be "A F 12.5".
Backup of the Hardware Clock
If there is a backup battery, the clock continues to run even after Power OFF. If the programmable
controller does not have a backup battery, the clock values will be set at "April 1, 1992, 12.00.00
o'clock, weekday: 4" when the clock is initialized after a Power ON. The default is the 24-hour time
mode. You should install a battery only during Power ON; otherwise, you would lose the clock data.
12-14
1 Error in setting entry
0 No error in setting entry
1 Enable the operating hours counter
0 Disable the operating hours counter
1 Transfer the settings
0 Do not transfer the settings
1 Error in setting entry
0 No error in setting entry
1 The set prompting time is reached
0 The set prompting time is not reached
1 Transfer the settings
0 Do not transfer settings
Meaning
Meaning
EWA 4NEB 812 6120-02b
S5-100U