Isochronous Mode - Siemens SIMATIC S7-1500 Manual

Configuring/address space
4.3 Manual operation (without technology object)
4.3.6

Isochronous mode

The technology module supports the "Isochronous mode" system function. This system
function enables position, counter and measured values to be acquired in a defined system
cycle.
In isochronous mode, the cycle of the user program, the transmission of the input signals
and processing in the technology module are synchronized. The output signals switch
immediately if the relevant comparison condition is met. 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 "Synchronous Cycle" (e.g. OB61) in this operating mode. The input and
output data are processed in the assigned OB.
The update time for the measured value is synchronized with the system cycle in a suitable
ratio and, if necessary, adapted in length. If you set "0", the measured value is updated once
per system cycle.
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
as well as status bits are 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)
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), the position or counter value and the measured value
i
Technology module TM PosInput 2 (6ES7551-1AB00-0AB0)
Manual, 06/2018, A5E03982218-AB