C# How can a counter pulse sync with an analog stair-step output

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Hi,

Now I'm using NI PCIe-6251 and BNC-2110.

I generated a stair-step signal and output it from analog output port AO1.

I want to make counter pulse signal which sync with the each step of the stair-step signal and output it from P2.4 port.

How can I generate such counter pulse signal and sync them by C# programming?

I want to know which class or function can be available to do this.

Thank you.