Siemens SIMATIC ET 200AL, System Manual

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Time-based IO basics
2.6 Technical implementation
High-precision input/output with Time-based IO
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Function Manual, 11/2019, A5E33454822-AC
2.6 Technical implementation
Introduction
The information below will help you better understand the core aspects of Time-based IO
and find out which SIMATIC functions are used to implement the described aspects.
Synchronization of involved modules (shared time basis)
The Time-based IO technology uses isochronous mode for all involved stations.
Isochronous mode enables multiple TIO modules to be synchronized to a shared time basis.
The basis of the shared time basis for the TIO modules is the relative time TIO_Time.
Additional information on isochronous mode is available in the Isochronous mode
( http://support.automation.siemens.com/WW/view/en/49948856 ) and PROFINET with STEP
7 ( https://support.industry.siemens.com/cs/ww/en/view/109755401 ) manuals.
TIO_Time
The TIO_Time is the central time basis to which all time stamps refer.
TIO_Time has the following properties:
● Shared time basis for all TIO modules which are synchronized with the TIO instruction
TIO_SYNC.
● The time starts counting again with each CPU startup.
● The TIO_Time has data type LTime (e.g. LT#14s830ms652us315ns).
● All valid time stamps refer to TIO_Time:
–
Input time stamps of the TIO modules are converted to the TIO_Time in the TIO
instructions TIO_DI and TIO_DI_ONCE.
– In the TIO instruction TIO_DQ, output time stamps are converted to the output time
stamp of the TIO modules.
● The value of TIO_TIME corresponds to the current time with respect to TIO instructions
and is updated with the call of TIO_SYNC. If you want an output to relate not to a
previous input time stamp but to the current time, you can use the value of TIO_TIME as
basis for the output time stamp. Example: Output of an edge in 20 ms:
TIO_DQ.TimeStampRE=TIO_SYNC_DATA.TLT#20ms)