Balluff BIS M-4 045 0 07-S4 Series, Operating Manual

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The sequence of the IO-Link communication is shown in the following diagram. Exchange alter-
nates between the input buffer and the output buffer. As soon as current data is pending in one
of the buffers, it is exchanged on the next input or output data cycle. The problem arises here
that the transmission times can vary greatly. If data is updated shortly before the start of the
respective exchange cycle, the transfer lasts just over 1 x cycle time. If, however, data is updated
shortly after the start of an exchange cycle, it lasts a maximum of 2 x cycle time.
The processing sequence of a command is shown on the next page using a read job of 9…16
bytes (2 x input buffer for read data) as an example.
Temporal relationship between primary bus system, IO-Link transmission and trans-
mission time
Assumption:
– Cycle time of bus system 4 ms (t1)
– Cycle time of IO-Link 8 ms (t2)
– Data transmission from the controller to the IO-Link device
Best case:
New data
4 ms
8 ms
IN OUT OUT
IN
Bus system
IO-Link
Transmission time ≈ t
1
+ 1/2 t
2
Worst case:
New data
4 ms
8 ms
IN OUT IN OUT IN OUT
Bus system
IO-Link
Transmission time ≈ t
1
+ 1.5 t
2
There is an offset between the bus system and IO-Link because the bus system and IO-Link
operate independent of one another (not synchronous).
9.6 Data
Transmission
Timing
9
Device Function
BIS M-4 _ _ IO-Link Device
Read/Write Device