Siemens SIMATIC ET 200SP - Clock Synchronization (TM Count and TM Posinput)

The basics of counting, measurement and position detection
2.2 Basics of counting, measuring and position input (TM Count, TM PosInput, Compact CPU)
Counting, measurement and position detection
Function Manual, 12/2017, A5E32009889-AG
75
2.2.15
Clock synchronization (TM Count and TM PosInput)
The technology module supports the "isochronous mode" system function in distributed
mode. This system function enables position, count and measured values to be recorded in
a defined system cycle.
In isochronous mode, the cycle of the user program, the transmission of the input and output
data and the processing in the module are synchronized with each other. The output signals
switch immediately if the relevant comparison condition is met. A change in the state of a
digital input immediately affects the planned reaction of the technology module and changes
the status bit of the digital input in the feedback interface.
Data processing
The data that was transmitted to the technology module in the current bus cycle via the
control interface takes effect when it is processed in the internal technology module cycle.
The position or counter value and the measured value and the status bits as well are
captured at the time T
i
and made available in the feedback interface for retrieval in the
current bus cycle.
Additional information
For a detailed description of isochronous mode, refer to the PROFINET with STEP 7 function
manual, which is available as download at Internet
(https://support.industry.siemens.com/cs/ww/en/view/49948856).