Synchronize Analog Input and Output in PCI 6259 example Error

Hi,

I have a PCI 6259.

I program example Figure 2 in http://www.ni.com/white-paper/3615/en/#toc3 to syncronize analog input and output.

But I recived this error:Error -89120

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Possible reason(s):

Source terminal to be routed could not be found on the device.

Make sure the terminal name is valid for the specified device. Refer to Measurement & Automation Explorer for valid terminal names.

Property: Start.DigEdge.Src
Property: Start.DigEdge.Edge
Source Device: Dev1
Source Terminal: ai/Start Trigger

Task Name: _unnamedTask<52>

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would you please help me for this problem