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Rules for Failsafe Operation of an S5-95F
18.19
SINEC L1 Safety Times
In a failsafe SINEC L1 system, the S5-95F differentiates between two types of safety times, i.e. the
SINEC L1 safety time for Receive and the SINEC L1 safety time for Send. The safety times may be
set separately for each data path (max. four different safety times).
Problems with the SINEC L1 Bus Master
When the SINEC L1 bus master is not functioning properly, e.g. because it is at STOP or because
of a restart following a POWER OFF/POWER ON sequence, failsafe frames might be delayed. If a
delay is excessive, the SINEC L1's watchdog timer containing the safety time for Receive could
expire (timeout). In this case, the S5-95F responds by going to STOP or by passivating the data
path, depending on what was specified in DB1.
18.19.1 SINEC L1 Safety Time for Receive
Definition:
The SINEC L1 safety time for Receive stipulates a time period for failsafe data paths
during which the receiving node must have received at least one valid frame.
The SINEC L1 safety time for Receive depends on the automated process and on the user
programs of the participating partners in the communications link. The value chosen as safety time
for Receive must be approved by the authorized inspector.
Discuss with the inspector the following points for each failsafe data path:
•
The SINEC L1 safety time for Receive
•
The system response when no valid frame is received within the time period stipulated as
SINEC L1 safety time for Receive.
Note
It is not necessary to send and receive at least one useful data frame within the SINEC
L1 safety time. If necessary, the operating system transmits additional test frames,
unbeknownst to the user, for the express purpose of monitoring the bus.
Interval for Receiving Frames
Note
Please note that the S5-95F cannot receive a new frame until it has processed the
previous one. You should therefore arrange communications between nodes so that
frames are received at least 100 ms apart, otherwise the S5-95F may not accept the
next frame.
18-38
S5-95F
EWA 4NEB 812 6210-02
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