Hi there.
Sorry about that, but again, this is more likely a serial issue, and also unrelated to the original topic, which means you want to create a new thread to continue this discussion. I recommend that if your problem is to ask about how to generate a pulse via a serial command, you post that in the Instrument Control section of our boards, since you're not dealing with our Motion Control VIs and hardware, but rather with other hardware.
http://forums.ni.com/t5/Instrument-Control-GPIB-Serial/bd-p/140
This board would be your best bet.
Ravi A.
National Instruments | Applications Engineer