Terminology

This is a summary, glossary about technical terms and abbreviations used in this documentation. Meaning and typical usecases are added to help understanding them.

Process Data - Valid, Invalid flag

Value of the ‘Valid’	Description / Meaning
0	Content of the Process Data is invalid
1	Content of the Process Data is valid

In other words, ‘valid’ is a synonym to reliable.
Two valid flags are used:

Process Data Input valid
Process Data Output valid

Note

Process Data Input Valid (flag)
This bit flag is provided by the connected IO-Link Device and received by the IO-Link Master

Routing: (flag) IO-Link Device --> IO-Link Master --> Application (PLC)

When input data is invalid (this flag is 0) then the received Process Data shall not be evaulated by the Application.
When this flag is set to 1, then the received data (the content) is valid, and can be evaluated by the Application.

UseCase:
When the connected IO-Link Device is already established the IO-Link communication but the device still in calibration or teach mode or ‘warm up’ therefore the provided measured data shall be ignore, shall not be processed.

Note

Process Data Output Valid (flag)
This bit flag is provided by the Application and transmitted via the IO-Link Master to the IO-Link Device

Routing: (flag) Application (PLC) --> IO-Link Master --> IO-Link Device

When output data is invalid (this flag is 0) then the sent out Process Data will not have any effect on the connected IO-Link Device.
When this flag is set to 1 then the sent out Process Data will be evaluated (executed) by the connected IO-Link Device.

UseCase:
If the Application is in teach mode or it went to a safe state, then Application may set this flag to 0 to force the connected IO-Link Device to ignore the Process Data Output. Some IO-Link device (eg: BNI IOL-302 Digital I/O Hub) is able to go set all output ports to a de-energized state based on this flag.

Example #1 of a weight measurement sensor
Data Path is Sensor –> PLC

Process Data Input valid flag example for a Digital I/O Hub
PD-OUT content	Valid flag	Result and Meaning for the Application
0x0000	1	Measured value is 0 gramm
0x0001		Measured value is 1 gramm
0x0009		Measured value is 9 gramm
0x00FF		Measured value is 255 gramm
0x0000	0	Measured value shall be ignored
0x0001
0x0002
0x000F

Example #2 of a Digital I/O Hub (actor)
Data Path is PLC –> Actor

Process Data Output valid flag example for a Digital I/O Hub
PD-OUT content	Valid flag	Result and Meaning for the Application
0x0000	1	All outputs are OFF
0x0001		Output 1 is ON
0x0002		Output 2 is ON
0x000F		Output 1, 2, 3, and 4 are ON
0x0000	0	Outputs are de-energised, or go to a state based on the IO-Link Device configuration
0x0001
0x0002
0x000F