B Description of the PROFINET Configuration File
288
Commissioning PC Stations - Manual and Quick Start
Release 5/2005
C79000-G8976-C156-07
The Cycle Time Parameter
This parameter will be configured in the user interface as of SIMATIC NET V6.1
with STEP 7/SIMATIC NCM PC V5.2 and higher.
Parameter Meaning
Syntax [PROTOCOL]
CycleTime=100
Purpose The scan cycle time specifies how often the OPC
server updates the values of the OPC items using
a new communication job.
Default 100 ms
Relationship between Cycle Time and Update Rate The “UpdateRate” parameter that can be set in the
user program specifies the shortest possible
interval for checking the values of the OPC items of
an active OPC group. When this interval elapses,
the server checks whether or not the values of the
active OPC items have changed.
The update rates used by the OPC Server for
SIMATIC NET are multiples of the cycle time
specified here during project engineering. The
maximum update rate (shortest interval) is the
same as the cycle time.
Relationship between the Set Protocol-specific
Cycle Times
Since the SIMATIC NET OPC Server can use
variables of different protocols at the same time,
the maximum update rate of the OPC server is the
highest value set for the scan cycle time for the
active protocols (those for which connections are
configured).
Example A scan cycle time of 100 ms is configured for
PROFInet. No other protocol is being used. 100 ms
is used by the OPC server as the minimum update
interval. The S7 protocol is now added and the
scan cycle time configured for this protocol is 500
ms. Result: The OPC Server now uses the value
500 ms as the minimum update interval for all
protocols.
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