Switching Off Et 200 And Reaction To Power Failure - Siemens SIMATIC S5 Manual

11.3 Switching off ET 200 and reaction to power failure

Switching off the The procedure for shutting down the ET 200 distributed I/O system is always
ET 200
as follows:
1. SET the STOP/RUN switch of the CPU to STOP.
2. Set the mode selector switch of the IM 308-C from RN to ST or OFF.
3. Switch off the power supply of the host.
4. Switch off the power supply to the DP slaves and
5. Set the STOP/RUN switch on each DP slave (if fitted) to STOP.
Warning
!
If response monitoring for DP slaves is deactivated and only the power
supply for the host is switched off, outputs may be inadvertently set.
In this case, set the IM 308-C to ST before switching off the power supply of
the host, or always proceed in accordance with the shutdown sequence
outlined above.
What do I do if the If you selected "QVZ = Yes" as the error-reporting mode in COM ET 200
power supply Windows, the CPU may refuse to restart when power is reapplied after a total
fails? power failure. The reasons are as follows:
Remedy: Your options are as follows:
ET 200 Distributed I/O System
EWA 4NEB 780 6000-02a
If the power supply to the slaves fails just before that of the DP master,
the CPU with QVZ goes to STOP.
When mains power is reapplied, the CPU remains in STOP on account of
QVZ.
Restart the CPU
or
program the appropriate OBs for QVZ, e.g. OB 23/24
or
select "PEU" as the error-reporting mode instead of "QVZ"
or
buffer the power supplies to the DP slaves in such a way that the CPU
always goes down before the DP slaves if a total power failure occurs.
IM 308-C – starting ET 200
11-15
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