Did you know...?
With the title „Did you know ..?” we introduced some new information about
IO-Link in the German SPS-MAGAZIN to you.
... that IO-Link has three transmission rates?
From the outset the fathers of the IO-Link specification had a wide range of field devices, including sensors, actuators, and much more, that should have communication capability thanks to IO-Link on their radar. Naturally the devices have completely different requirements and conditions with regard to available processor performance. Thanks to the three defined transmission rates – 4.8 kbps, 38.4 kbps, and 230 kbps – developers always find a transmission rate adapted to the IO-Link device. The device specifies the utilized transmission rate in IO-Link. The IO-Link master handles all three transmission rates. When establishing a connection, the master initially uses the highest transmission rate and then the next lower transmission rate until the connection is actually established.
A much-discussed issue is whether IO-Link should be classified as a slow or fast interface. As the following example shows, concerns about the transmission rate are totally unfounded: In the case of an IO-Link measuring sensor that operates with 14-bit resolution, the measured values are transmitted over the IO-Link system as 2 bytes of process data. IO-Link provides not only the pure cyclic process data channel but also an acyclic channel for
on-request data, for example, for diagnostics and parameter assignment.
A typical scenario for the indicated IO-Link sensor is that 2 bytes of process data and 1 byte of on-request data are transmitted. At 230 kbps, also referred to as COM3, a complete transmission cycle takes only 0.46 ms. At 38.4 kbps (COM2), it takes 2.3 ms. IO-Link masters are typically multi-channel. The described action runs in parallel for all channels. In the above-described example, an 8-channel master makes available 8 measured values plus the
on-request data bytes to the fieldbus level every 0.46 ms (2.3 ms for COM2). Compared with an assumed typical cycle time on fieldbuses of 5 ms, there are thus no bottlenecks as a result of IO-Link.
Here you can find information about the advantages of IO-Link and
here about the manufacturers.
