Greetings,
When using an example, such as the Generate Pulse Train (DAQ-STC).vi, the best place to go for running instructions and signal connections is the Documentation found by going to File -> VI Properties and pulling down the menu to Documentation.
You will most likely be using the board's internal timebase and, as such, do not need to connect anything to the counter's SOURCE pin. You will find that you can optionally gate the pulse generation. If you just want to simply generate a continuous pulse train and not stop or pause it until the user clicks the Stop button, then all you need to do is open this VI, enter the device number for your DAQ card, specify the counter you will be using (0 or 1), and enter your desired frequency and duty cycle.
The pulse will be generated on the specified counter's OUT pin. A connection from the OUT pin to your external hardware is the only physical connection you should have to make.
To find out the pin number for the OUT pin you will have to look up the cable-pinout for your specific DAQ card. This pinout is in the User's Manual. I believe you misquoted your hardware since we don't make a PCI-6020E. Therefore, I cannot double-check the pins for you.
Regards,
Justin Britten
Applications Engineer
National Instruments
