Trigger hold off

[rpodsim]

I've just recieved the Virtualbench for a demo/loan and setup to look at a serial data stream. I ran into the problem of the trigger not holding a stable position, it would trigger on any edge in the stream instead of the starting edge. Usually, I would set the Oscope to a hold off period slightly longer then my data stream, but I can't figure out how or if this is possible with the VirtualBench. I've tried setting it up using both the digital and analog MSO inputs and both behave the same. I've looked the LabVIEW API and didn't see anything either.

Does anyone knows how or if it's possible to do something like this? Note: the data stream packets last ~50usec, transmitted every 100-300uSec. If I slow down the transmit rate I don't have a problem with the trigger.

Thanks

[WilliamEarle]

Hi Ryan,

Pre-trigger time is a similar idea to hold-off in the VirtualBench API. After starting an acquisition, the MSO hardware ignores trigger conditions for the pre-trigger time.

In the LabVIEW API, you can control it directly. It's an input to "MSO Configure Timing".

In the application, you can control it by moving the trigger position on the screen (to the right is more pre-trigger time). In the application, the amount of pre-trigger time is based on the time per divison as well, so if you want an exact number like 50uS, it might be easier to set it through the LabVIEW API.

Regards,

William Earle

Software Engineer

NI R&D