Siemens SINAMICS S120 Function Manual page 777

Update cycles and send cycles for RT classes
Definition of the update time / send cycle:
If we take a single IO device in the PROFINET IO system as an example, this device has
been supplied with new data (outputs) by the IO controller and has transferred new data
(inputs) to the IO controller within the update time. The send cycle is the shortest possible
update cycle.
All cyclic data is transferred within the send cycle. The actual send cycle that can be set
depends on various factors:
● Bus load
● Type of devices used
● Computing capacity available in the IO controller
● Supported send clocks in the participating PROFINET devices of a synchronization
The table below specifies the reduction ratios which can be set between the send cycle and
the update times for IRT "high performance", IRT "high flexibility", and RT.
Table 10- 64 Settable send cycles and update cycles
Send cycle
Range 250, 500,
"even" 1000 µs
1)
2000 µs
4000 µs
Range 375, 625, 750,
"uneven" 875, 1125,
3)
1250 µs ...
3875 µs
(increment
125 µs)
Note
There is no intersection between the send cycles for the "even" and "uneven" ranges!
Drive functions
Function Manual, (FH1), 01/2013, 6SL3097-4AB00-0BP3
domain. A typical send cycle is, e.g. 1 ms.
Reduction ratio between update and send cycles
RT
IRT "high flexibility"
1,2,4,8,16,32,64,128,256,512
1,2,4,8,16,32,64,128,256
1,2,4,8,16,32,64,128
Not supported
10.3 Communication via PROFINET IO
4)
5)
Communication
IRT "high performance"
1,2,4,8,16
2)
1,2,4,8,16
2)
1,2,4,8,16
2)
1
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