Siemens SIMATIC ET 200SP Manual page 18

Product overview
2.2 Functions
Isochronous mode of I/O data
I/O data, transmission cycle via PROFINET IO, and the user program are synchronized to
achieve maximum deterministics. The input and output data of distributed I/O modules in the
system is simultaneously collected and simultaneously output. The constant PROFINET IO
cycle forms the corresponding clock generator. The interface module supports isochronous
mode of I/O data for the modules starting at 125 µs. The IO device can exchange
isochronous process data with a maximum of one IO controller.
Note
If the IO controller cannot access a module (for example, module pulled, activated
configuration control without written control data record), cycle time violations may occur with
activated isochronous mode in the synchronous cycle interrupt OB (OB61). The time error
OB (OB80) is called in the event of a cycle time violation.
This behavior is associated with updating the process image by means of the "SYNC_PI"
(SFC126) and "SYNC_PO" (SFC127) instructions and depends, among other things, on the
set cycle time and the configuration limits.
Note
Isochronous mode restrictions with IM 155-6 PN HS
Isochronous mode of I/O data in combination with the following functions is not possible with
the interface module IM 155-6 PN HS:
• PROFIenergy
You can find more information on this topic in the STEP 7 online help and
● As of STEP 7 V14, in the PROFINET with STEP 7 V14
(http://support.automation.siemens.com/WW/view/en/49948856) function manual
● As of STEP 7 V5.5, in the PROFINET System Description
(http://support.automation.siemens.com/WW/view/en/19292127) system manual
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IM 155-6 PN HS interface module (6ES7155-6AU00-0DN0)
Manual, 09/2016, A5E34928647-AA