Null data indicates a Signal has no defined value. This is not the same as value of zero. In a TestCase, null data is represented by square gray dots:

Null data dots before a transition

Null data dots before a transition

Numeric response Signals have null data between power on and their first transition. It is also possible for a numeric response Signal to change from a defined value to null data after a system reset. See System Reset.

For expected response Signals, you can create a transition to null data manually using the Edit Transition dialog. The Accept Results command may also create null data in expected results.

Example

NullData-afterReset

In this example, Value2, a numeric message-based Signal, has null data at power on (time 0). Each time its parent message (MsgHazard) is received, a value is assigned. An MxV Module Reset is asserted at 10 seconds, which resets Value2 to null data. When MsgHazard is received again, a value is assigned again.

Related Topics:

System Reset

Editing Message Fields (message-based signals)

Viewing Signals—No Defined Value (null data)