S5-95F
Rules for Failsafe Operation of an S5-95F
18.16
Programmer-Based Operator Input Functions
For reasons of safety, the programmer-based operator input functions are restricted in safety mode.
In this mode, only Read functions may be invoked on the programmer. Only the parameter control
DB can be both read out and modified via the programmer in safety mode when the PLCs are at
STOP.
Parameter Control DB
In safety mode you can use the programmer function ”Output block” to alter the parameter control
DB when the PLCs are at STOP. This DB allows you to specify certain system parameters "during
operation".
Of course, these parameters must be run through a so-called filter routine in the user program for
reasons of failsafety.
The authorized inspector must examine and approve the filter routine just as he must all other blocks
in the user program.
You must enter the number of the parameter control DB in DB1.
STOP via Programmer Input Command
Note
There is no interlock feature to prevent you from switching the PLC from STOP to RUN,
and you can do so simply by pressing a button on the programmer. For this reason, the
STOP initiated via the programmer may not be regarded as safety condition.
When maintenance is necessary, you should therefore always switch the S5-95F off via
its own switch.
Increase in the Response Time Due to Programmer Function
Note
When executing the STATUS function, the S5-95F processes the blocks in a special
mode; the blocks' runtimes are thereby considerably increased, and are operation-
dependent. Note that the response time is also increased. You should therefore keep
your blocks as short as possible.
The S5-95F monitors the PLC cycle time, and makes sure that the response time is
never more than double the maximum PLC cycle time specified with COM 95F.
EWA 4NEB 812 6210-02
18-33
