Time Sequence Of Synchronization - Siemens SIMATIC PROFINET Function Manual

5.7.4

Time sequence of synchronization

From reading-in of input data to outputting of output data
The basic time sequence of all components involved in synchronization is explained in the
following:
● Reading-in of input data in isochronous mode
● Transport of input data to the IO controller (CPU) via the PROFINET subnet
● Further processing in the isochronous application of the CPU
● Transport of output data to the outputting IO device via the PROFINET subnet
● Outputting of output data in isochronous mode
T_DC Data cycle (Time_DataCycle)
T Time for reading in the input data
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T Time for outputting the output data
O
Figure 5-67 Time sequence of synchronization
The start of the I/O read cycle is advanced by the amount of a bias time T
all input data available for transfer on the PROFINET IO line at the start of the next
PROFINET IO cycle. T
are read in. T
backplane bus times, and the like. The bias time T
user. We recommend automatically assigning the bias time T
The PROFINET IO line transports the input data to the IO controller. The application can be
started synchronized to the cycle, i.e., the isochronous mode interrupt OB is called after a
parameterizable delay time. The user program in the isochronous mode interrupt OB decides
the process reaction and provides the output data in time for the start of the next data cycle.
The length of the data cycle is always configured by the user.
PROFINET with STEP 7 V14
Function Manual, 09/2016, A5E03444486-AG
is the "flashlight" for the inputs; at this instant all synchronized inputs
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is necessary in order to compensate for analog-to-digital conversion,
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5.7 Isochronous mode
can be configured by STEP 7 or by the
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of STEP 7.
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Functions
in order to make
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