Siemens SIMATIC ET 200AL, System Manual

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Functions
5.7 Isochronous mode
PROFINET with STEP 7
220
Function Manual, 05/2021, A5E03444486-AL
5.7.3 Time sequence of synchronization on PROFINET IO
Introduction
On PROFINET IO, you can isochronously operate I/O modules in distributed I/O systems on a
CPU, e.g. in distributed I/O systems ET 200SP, ET 200MP.
Like the I/O modules, the interface modules of the I/O systems must support isochronous
mode.
From reading in input data to outputting output data
The basic time sequence of all components involved in synchronization is explained below:
① Measured value acquisition in the process
② Isochronous read-in of input data
③ Transport of input data to the IO controller (CPU) via the subnet
④ Further processing in the isochronous application of the CPU
⑤ Transport of output data to the outputting IO device via the subnet
⑥ Isochronous output of output data
T_DC Data cycle (Time_DataCycle)
T
I
Time for reading in the input data
T
O
Time for outputting the output data
T
V
Configured delay time
Figure 5-72 Time sequence of synchronization on PROFINET IO