Think about how your project would work with the USB-6009.
You need to respond to a trigger signal. You did not specify the voltage, rise time, or duration of the trigger signal. For this example let's assume that you have a logical signal which goes from 0 V to +5 V in a few ns and stays high for 1 second. The response will be a digital output.
With the 6009 you can use an analog input with a digital trigger or software timed digital inputs. Since the digital output is software timed, let's consider the digitally triggered analog input.
Your program will set up the analog input to acquire one sample when the digital trigger occurs. Ignoring the set up process which can take place long before the trigger hand has no effect on the response timing, this is the way things will happen. At each point I show in parentheses which software or hardware process is involved.
DAQ Read request (VI). Pass request to DAQ Driver (OS). Pass request to hardware (DAQ Driver). Wait for trigger and acquire 1 sample (HW). Return sample message (DAQ Driver). Pass message to DAQ Read (OS). Receive and process sample (VI). DO Write request (VI). Pass request to DAQ Driver (OS). Pass request to hardware (DAQ Driver). Write DO (HW).
Things in the VI category can happen in nanoseconds to very long times, depending on how you write your program. For this example a few microseconds is probably a reasonable estimate. Similarly for single point data the DAQ Driver parts are probably in the microsecond scale. The OS can take as much time as it wants. You have no control unless you are using a real-time, deterministic OS. Even Linux can have unpredictable latencies. On any desktop OS the latencies may often be in the few milliseconds range and can on rare occasions be much longer. The hardware latnecy is probably in the microsecond range.
Lynn
