Pattern I/O Using Start & Stop Trigger

[cjmoran]

I would like to output the same block of data repeatedly (1000 patterns as an example) using the PCI-6534 Pattern I/O mode. I would like the 1000 samples to come out immediately following a low-to-high transition on the STARTTRIG input. After the first 1000 samples are completely sent (all 1000), I would like to again output the same 1000 samples, etc. I am also planning on using the STOPTRIG. On a high-to-low STOPTRIG transition, I would like to complete the present pattern output (output all 1000 samples) and then stop.

My manual says that, "When using a start and stop trigger, transfer starts upon receiving a trigger on the start trigger line (ACK/STARTTRIG pin) and ends upon receiving a trigger on the stop trigger li
ne (STOPTRIG pin) and a predetermined amount of pretrigger and postrigger data is saved in the buffer... If the stop trigger arrives before all the pretrigger data is acquired [or sent in my case], NI-DAQ returns an error."

Will I get all 1000 samples at the output even if I receive a STOPTRIG falling edge during a block output sequence? Am I going to get an NI-DAQ error of some sort? I don't know how to interpret this statement. I want to finish with the pattern output (all 1000 blocks before I stop).

I am using one signal for both the STARTTRIG and the STOPTRIG. When high, I want to output 1000 block patterns continuously. When low, I want to finish with the present sequence and then wait until my signal again goes high. I must not stop a 1000 block pattern sequence in the middle. That is why I have this question. If anyone knows a better way of doing this or has any insight, please let me know.

Thanks.

[Annette Perez]

CJMoran,

When having a start and a stop trigger, instead of starting the acquisition when the software stars, this method waits for the start trigger before acquiring data. when the strop trigger is received, x amount of pre-trigger and y amount of post-trigger data is saved. If the stop trigger occurs before the start trigger is received, it is ignored. But if the trigger occurs before x amount of pre-trigger data is received, you will always receive an error message.

So, as long as the trigger is not received before the x amount of pre-trigger data, you should be able to get the 1000 points and will have no errors in your program.

Good luck!