Isochronous Mode - Siemens SIMATIC S7-1500 Manual

4.2.4

Isochronous mode

The technology module supports the "Isochronous mode" system function. Position and
counter values can be acquired in a fixed system cycle with this system function.
In isochronous mode, the cycle of the user program, the transmission of the input signals
and processing in the technology module are synchronized. A status change of a digital input
immediately triggers the specified reaction of the technology module and the change of the
status bit of the digital input in the feedback interface.
Use an OB of type "MC-Servo" in this operating mode. Isochronous mode is needed when
using the output cam and cam track technology objects. When the measuring input
technology is used in combination with hardware digital input DI1, isochronous mode is not
needed.
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. At
the time the input data is read in (T
acquired and made available in the feedback interface for retrieval in the current bus cycle.
Isochronous mode parameters
In isochronous mode, the following parameter can affect the isochronous mode parameters
of the sync domain.
● Filter frequency
● Frame length
● Transmission rate
● Monoflop time
● Parity
Because the isochronous mode parameters are not checked in RUN, overflows can occur if
you change one or more of the indicated parameters in RUN. To prevent overflows, select
the option with the largest time required in the offline parameter assignment.
Additional information
You can find a detailed description of isochronous mode in the following:
● Function manual Isochronous Mode (STEP 7 (TIA Portal) V15.1 or higher) available for
download on the Internet
(https://support.industry.siemens.com/cs/ww/en/view/109755401)
● Function manual PROFINET with STEP 7 available for download on the Internet
(https://support.industry.siemens.com/cs/ww/en/view/49948856)
Technology module TM PosInput 2 (6ES7551-1AB00-0AB0)
Manual, 06/2018, A5E03982218-AB
4.2 Position input for ""Motion Control"" technology object
), the position or counter value as well as status bits are
i
Configuring/address space
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