Technical data

Communication
9.4 Communication via PROFINET IO
Function Manual
Function Manual, 06/2012, 6SL3097-4AB10-0BP4
665
Update cycles and send cycles for RT classes
Definition of 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 are 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
domain A typical send cycle is e.g. 1 ms
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 9- 40 Settable send cycles and update cycles
Reduction ratio between update and send cycles Send cycle
RT
IRT "high flexibility"
4)
IRT "high performance"
250, 500,
1000 µs
1,2,4,8,16,32,64,128,256,512 1,2,4,8,16
2)
2000 µs 1,2,4,8,16,32,64,128,256 1,2,4,8,16
2)
Range
"even"
1)
4000 µs 1,2,4,8,16,32,64,128 1,2,4,8,16
2)
Range
"uneven"
3)
375, 625, 750,
875, 1125,
1250 µs ...
3875 µs
(increment
125 µs)
not supported 5) 1
Note
There is no intersection between the send cycles for the "even" and "uneven" ranges!