Siemens SIMATIC S5-115U, User Manual

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Integral Real-Time Clock S5-115U Manual
13.3 Structure of the Status Word
The status word can be scanned to detect, for example, errors in the entry of clock settings, or
alternatively, specific bits can be changed in the status word to disable or enable transfer or read
operations.
The response of the CPU when changing from RUN to STOP or during POWER OFF can be deter-
mined with the bits (flags) reserved for this purpose.
• The status word can be located in the flag area or in a data block. The location must be
defined in system data words 9 and 10.
• The integral clock runs independently of the mode set.
Access to the clock data area is dependent on the mode set and the states of bits 4 and 5 of
the status word (cf. Table 13-6). You can set or reset these bits with "S" or "R" operations in
the control program.
When monitoring the program with an operator panel (e.g. the OP 396), it is advantageous to
have the CPU update the clock (current date) also in STOP mode.
• The "Transfer settings" bits (bits 2, 10 and 14 in the status word) are reset by the operating
system if
- the settings have been transferred
- the settings have not been transferred because they were outside the permissible range. In
this case, the relevant error is set (bits 0, 8 and 12 of the status word).
• The "Transfer settings" bits (bits 2, 10 and 14 of the status word) are not reset by the opera-
ting system if
- the system data for the clock are incorrect or not available
- the clock data area is too small
- the clock is defective (hardware error).
• The bits of the status word are divided into
- clock flags
- operating system flags
- operating hours counter flags
-
prompting time flags.
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EWA 4NEB 811 6130-02b