Siemens SIMATIC ET 200S Operating Instructions Manual page 231

Isochronous Encoder Value Detection
Isochronous encoder value detection is carried out automatically when the equidistant bus
cycle is activated in the DP master system and the DP slave is synchronized to the bus
cycle.
The 1SSI initiates the transmission of a message frame in every bus cycle at time T
as the configured maximum encoder sampling rate does not result in a reduction.
The 1SSI processes the transmitted encoder value isochronously to the bus cycle.
Technological Functions
Operating Instructions, 02/2007, A5E00124867-05
1SSI
4.6 Functions of the 1SSI
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