Siemens SIMATIC S5-100U, System Manual

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S5-100U The Integral Real-Time Clock
If your inputs differ from the ones described, the operating system outputs error messages that are
displayed in the status word. The operating system resets error messages displayed in the status
word the next time you set the clock, prompt time, or the operating hours counter, if the new
settings are within the definition range. See section 12.5.
If you do not wish to modify one of the setting values, you can enter at its place XX (ASCII code) in
DB1, or FF (hexadecimal code) when you are programming in the system data.
If the clock data area is located at the end of other areas (flags, data blocks, inputs, and outputs)
and there is insufficient memory space available for the clock data area, the amount of clock data
transferred is only as much as will fit in the area available. Settings are not accepted if they lie
outside of the available space.
• If clock data is located in the non-retentive flag area, then the following two events occur:
- All the settings are lost after Power OFF and cold restart.
- The time the last switch from RUN to STOP occurred is lost.
• Remember that you can decide where to locate the clock data area. The word numbers listed in
Table 12-3 are relative.
- If your clock data area is located in a data block and does not begin with data word DW0 but
DWX, then you must add the value X to the word number shown in Table 12-3.
Example: Your clock data area begins with DW124. The data for the time and date is then
stored in DW124 to DW127.
- If you locate your clock data area in the flag area beginning with flag word 0, then you must
multiply the appropriate data word number listed in Table 12-3 by a factor of 2 to obtain the
appropriate flag word address.
Example: You locate your clock data area in the flag operand area beginning with flag
word 0. Data for the operating hours counter is then stored beginning with the
FW24 address.
- If your clock data area does not begin at flag word 0, you have to add the beginning value to
the word number shown in Table 12-3.
EWA 4NEB 812 6120-02b
12-11