S5-95F
Rules for Failsafe Operation of an S5-95F
Special Features of Standard Value Formation for Onboard Counters
Safety Note
In the case of discrepancies in onboard counters, the system operates in part with
counter values ascertained over a single channel. If you choose formation of a standard
value with AND, OR or OLD VALUE as system response to onboard counter
discrepancies, you may not use the counter values for failsafe functions following a
counting error.
18.10.1 Passivating of I/Os
If your process consists of several independent subprocesses, you have the option of passivating
the I/Os belonging to a signal group.
The passivation of I/Os is understood to mean a software and hardware shutdown of those I/Os. You
may passivate I/Os only when they belong to an independent, self-contained subprocess; this must
first be carefully examined and ascertained to be the case.
The S5-95F enters an identifier in data words DW35 and DW36 of system event data block DB254
for each pasasivated signal group. These entries can be evaluated in the user program, and the
program written to respond accordingly.
The passivation of failsafe I/Os has the following effect:
•
DIs
Immediate removal of the PII entry for the relevant DI
(other than
interrupt DIs)
•
OB2 interrupt DIs:
Immediate resetting of the diagnostic bytes, immediate resetting of DQ
byte 32, OB2 will no longer be invoked
•
OB3 interrupt DIs:
Immediate resetting of the diagnostic bytes, immediate resetting of the PII
entry for the relevant interrupt DI bytes
•
DQs:
Immediate removal of the PIQ entry for the relevant DQ, resetting of the
DQ following a direct access operation or end of cycle
Note
Failsafe technology requires that the load voltage for passivated I/Os be interrupted, at
the latest, when the secondary error occurrence time has expired. When using an S5-
95F, the interruption need not be organized at the user level; instead, the S5-95F acts
autonomously, interrupting the voltage via auxiliary shutdown paths (third and fourth
paths).
EWA 4NEB 812 6210-02
18-17