Sending The Freeze And Sync Control Commands - Siemens SIMATIC S5 Manual

9.5 Sending the FREEZE and SYNC control commands

What is a control The IM 308-C can send simultaneous commands to a group of DP slaves in
command? order to synchronize them.
The FREEZE and SYNC control commands enable you to synchronize
groups of DP slaves in response to events.
What is FREEZE? When it receives the FREEZE control command from the DP master, the DP
standard slave freezes the current status of the inputs and transfers these
inputs cyclically to the DP master.
After every new FREEZE control command, the DP standard slave again
freezes the status of the inputs.
The freeze remains in effect and the input data is not again updated until the
DP master sends the UNFREEZE control command.
What is SYNC?
When it issues the SYNC control command to a DP standard slave, the
DP master is instructing the DP standard slave to freeze the states of the
outputs at their current value. When it subsequently receives telegrams, the
DP standard slave stores the most recent output data, but the output status
remains unchanged.
After every new SYNC control command, the DP standard slave sets the
outputs which it last received.
Cyclic updating of the outputs does not resume until the DP master sends the
UNSYNC control command.
Preconditions
The FREEZE and SYNC control commands are not effective unless you have
structured the DP slaves in groups with the aid of COM ET 200 Windows.
You must know which DP slave is assigned to which group and you must be
in possession of the group number before you can issue these control
commands. You can check these numbers in the "group membership" listing.
When you send a control command, you must use the FB IM308C to
ascertain whether the control command has already been broadcast to all the
DP slaves concerned. Only then can you continue processing the
inputs/outputs in question.
Issuing control
In order to issue control commands to the groups of DP slaves, you must set
commands
FCT = GC and the GCGR parameter to suit the control command in question.
See Section 9.7 for the remaining parameters.
Result: In accordance with the parameter settings, the FB IM308C sends the
control commands to the groups of DP slaves.
ET 200 Distributed I/O System
EWA 4NEB 780 6000-02a
IM 308-C – addressing, diagnostics and use of the FB IM308C
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