Hi Wen,
You can do this using a counter output task. You will want to set the counter to output continuously. You can route the TTL signal to a PFI line and then set the output task to output a pulse based upon ticks. For example, you could set the task to be idle low and have 98 ticks low and 2 ticks high (total of 100 TTL ticks).
Here is a picture of how this would be done in LabVIEW:
The equivalent C function calls would be:
DAQmxCreateCOPulseChanTicks
DAQmxCfgImplicitTiming
DAQmxStartTask
DAQmxGetTaskComplete
DAQmxClearTask
In .Net you will want to look at the CODataTicks Structure.
Regards,
Jennifer O.
Applications Engineer
National Instruments
Message Edited by Jennifer O on 12-14-2006 04:10 PM