Hey folks,

I have a question about the acylic data in IO-Link. Is there somebody out there, who can explain this to me, cause I think I don´t get it. 

I read the specification, and there are the m-sequences. There is shown, that the on-request data is transmitted with the process data. Does it work so? And do these bytes for on request data are reserved for the transmission?

Hello Leinad;

I hope I understand your question correctly:

IO-link by itself only has cyclic exchanges with the slaves on its network.

However, in Siemens' world, IO-Link masters are a subnet from a Profibus-DP (or Profinet) network, and the DP master/Profinet IO-Device uses acyclic exchanges to parametrise the IO-link master.

Please study this FAQ for more details:

Acyclic Read and Write with the IO-Link Library

Hope this helps,

Daniel Chartier

Hello dchartier,

Thank you for your answer. I hope I got it. I make an example, could you tell me if this is right?

There is a IO-Link device connected to a IO-Link master and the master has a gateway to the bussystem.  The device is in operate mode. The device transmits the process data cyclic according to the m-sequence. Then suddenly an Error occurs in the Device. The Device set the Eventflag in CKS and sends the cyclic data to the Master. The master reads with on- request data the event memory of the device. Then the Master sends a message to the gateway application. (How much byte is this Message?)

Is this right so far?

Poorly I haven´t got a IO-link system right now, so I can´t try out.

Hello Leinad;

My (very small) experience with IO-Link masters and devices, both from Siemens and other controller families, reveal no conscious connection to M-sequences on an IO-link device though programming.

M-sequences codify the data exchanges between the device and the master, and I believe they are completely integrated in the IODD file of the IO-Link device that you load into the master at configuration time. They then become transparent to the user and are part of the cyclic data exchanges.

The IO-Link libraries provided by Siemens are used to acyclicly read and write parameters to the IO-Link master and the devices through function blocks provided by Siemens. You can also use them to read diagnostics from the IO-Link devices upon request (though function block calls). See the following documentation:

IO-Link System manual v3.0 (Complete edition)

Hope this helps,

Daniel Chartier

Hello dchartier,

Thank you very much for your answer.

I know there is a library which I can use to program an access to the master and the device. I need further information for my project, so I have to go deeper in detail.   I have to analyze how much bytes are send to profinet-bus. I need to check the worst case total sum of bytes.  The master is able to send the process data and on request data to the gateway application(I use Profinet and a siemens PLC).  I have 3 CMMO motorcontroller of Festo and 1 valve terminal of Festo too. CMMO´s have 16 Byte processdata and the valve terminal up to 24 Bytes. In addtion it is possible to send On-request data and Event-data to the application and I need to know if I could plug this 4 devices on one master. I have to count how much byte are in total send via profinet to the application.

Hello Leinad;

As I stated earlier, I have had only superficial interaction with IO-Link devices up to now, and none with Festo valves.

I am afraid that the questions you ask will require reading Festo documentation and experimenting on your project when you actually have your equipment for tests.

Hope this helps,

Daniel Chartier