Communication
11.2 PROFINET
S7-1200 Programmable controller
938 System Manual, V4.2, 09/2016, A5E02486680-AK
Setting of the real-time properties
STEP 7 calculates the communication load and thus the resulting update times. You must
enter the number of project-external IO controllers in the project in which the PROFINET
interface of the shared device is assigned to the IO controller so that a calculation is possible
with shared device configurations.
The maximum possible number of IO controllers for the shared device depends on the
device. This number is stored in the GSD file of the shared device.
You can set a very short send clock (minimum of 1 ms) with an S7-1200 CPU as IO
controller. The send clock can be shorter than the shortest send clock supported by the
shared device. In this case, the shared device is operated by the IO controller with a send
clock that it supports (send clock adaptation).
Example: A CPU supports send clocks starting from 1 ms. A configured IO device supports
send clocks starting at 1.25 ms; another IO device supports send clocks starting at 1 ms. In
this case, you have the option of setting the short send clock of 1 ms for the CPU. The CPU
operates the "slow" IO device with the send clock of 1.25 ms.
Rules for the configuration
● IO controllers that use the shared device are created in different projects. In each project,
care must be taken that the shared device is configured identically in each station. Only
one IO controller may ever have full access to a submodule. Inconsistencies in the
configuration result in a failure of the shared device.
● I/O addresses of a module or submodule can only be edited if a module or submodule is
assigned to the IO controller in the same project.
● The shared device must have the same IP parameters and the same device name in
each project.
● The send clock must be identical for all IO controllers that have access to the shared
device.
● The S7 subnet ID of the subnet to which the shared device is connected must be identical
in all projects.
● The following functions are only available if the PROFINET interface of the shared device
is assigned to the local IO controller:
– Prioritized startup
– Parameter assignment of the port properties
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