Siemens SIMATIC ET 200SP Manual page 24

Product overview
2.2 Functions
Isochronous mode
The technology module supports the "isochronous mode" system function in distributed
mode. This system function enables position, counter 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 signals
and processing in the technology module are synchronized. 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 (Page 51).
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, if required, the measured value and the status bits as well
are captured at the time T
current bus cycle.
In isochronous mode, there is always data consistency across all bytes in the feedback
interface.
Additional information
A detailed description of the isochronous mode is available in the PROFINET with STEP 7
function manual as download on the Internet
(https://support.industry.siemens.com/cs/ww/en/view/49948856).
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and made available in the feedback interface for retrieval in the
i
Technology module TM PosInput 1 (6ES7138-6BA00-0BA0)
Manual, 04/2016, A5E33015755-AC