Data Acquisition Toolbox

Event Types

The analog output event types and associated action properties are described below.

Table 6-9: Analog Output Action Properties  

Event Type	Property Name
Run-time error	RuntimeErrorAction
Samples output	SamplesOutputAction
	SamplesOutputActionCount
Start	StartAction
Stop	StopAction
Timer	TimerAction
	TimerPeriod
Trigger	TriggerAction

Run-time Error Event.   A run-time error event is generated immediately after a run-time error occurs. This event executes the action function specified for RuntimeErrorAction. Additionally, a toolbox error message is automatically displayed to the MATLAB workspace. If an error occurs that is not explicitly handled by the toolbox, then the hardware-specific error message is displayed.

The default value for RunTimeErrorAction is daqaction, which displays the event type, the time the event occurred, the device object name, and the error message.

Run-time errors include hardware errors and timeouts. Run-time errors do not include configuration errors such as setting an invalid property value.

Samples Output Event.   A samples output event is generated immediately after the number of samples specified by the SamplesOutputActionCount property is output for each channel group member. This event executes the action function specified for SamplesOutputAction.

Start Event.   A start event is generated immediately after the start function is issued. This event executes the action function specified for StartAction. When the action function has finished executing, Running is automatically set to On and the device object and hardware device begin executing.

Stop Event.   A stop event is generated immediately after the device object and hardware device stop running. This occurs when:

• The stop function is issued.
• The requested number of samples is output.
• A run-time error occurs.

A stop event executes the action function specified for StopAction. Under most circumstances, the action function is not guaranteed to complete execution until sometime after the device object and hardware device stop running, and the Running property is set to Off.

Timer Event.   A timer event is generated whenever the time specified by the TimerPeriod property passes. This event executes the action function specified for TimerAction. Time is measured relative to when the device object starts running.

Some timer events may not be processed if your system is significantly slowed or if the TimerPeriod value is too small. For example, a common application for timer events is to display data. However, since displaying data is a CPU-intensive task, some of these events may be dropped. To guarantee that events are not dropped, you may want to use the SamplesOutputAction property.

Trigger Event.   A trigger event is generated immediately after a trigger occurs. This event executes the action function specified for TriggerAction. Under most circumstances, the action function is not guaranteed to complete execution until sometime after Sending is set to On.

Configuring Events and Actions

Recording and Retrieving Event Information