Transmission errors can occur for plenty of reasons, in general, a cable fault or a power surge can momentarily conflict with transmissions.

If an error is detected, the letter attempts transmission up to an additional two times.

Only after the transmission has lost for the third time does the IO-Link master recognize a communication failure. Upon recognizing this, the master will send the massage failure to the higher-level controller. This alert operators or maintenance staff of the issue, so they can physically attend to and fix the problem.

These are the four types of transmission that An IO-Link has  :

+ Value Status                    + Process Data

+ Events                             + Device Data

1. IO-Link Process Data Transmission

Process Data is transmitted cyclically, which means automatically, at regularly defined intervals. Up to 32 bytes of process data can be treated, and it’s determined by the high-level controller.


2. the Value Status of Transmission of an IO-Link 


it indicates whether the Process Data is valid or not.

3. Device Data Transmission of an IO-Link 

The Device Data holds detailed information about a device. such as the serial number or version number and more like parameters or diagnostic information are able to be retrieved from each IO-Link device.

Device Data is transmitted acyclically when the request from the IO-Link master is activated. in other words the process not automatically transferred but will be transferred after an ask from the Master.

4.  Event Transmission of IO-Link

An IO-Link slave is able to trigger an event, which in turn signals the presence of an Event to the IO-Link Master.

An example of an event is an error or warning message that indicates that something not working properly, for example, a short circuit, or overheating.

This information can be used to display indicators or messages on HMI (Human Machin Interface) devices, such as error messages signaling a wire break or a communication failure.

The delivery of device parameters and events occurs separately from the cyclic transmission of Process Data. This means they do not impact on each other, so critical and important messages do not have to queue until already buffered messages are sent.