huge delay when PCI-6534 starts

[Vasilich2004]

Hi,

To simplify my question I used standart example - Buffered Pattern Output.vi . In the example DIO Start.vi (Actually Digital Buffer Control.vi) gives huge (> 200 msec) delay.

Currently, I used module in internal clock. I will use with external clock.

Please, any ideas!

Andrei.

[Elijah_K]

Is the delay you're experiencing a product of the steps necessary to create the task?  All of the VIs that are used to create a task and setup timing to require a small amount of processor time that you cannot reduce.

Are you interested in setting up your task to be triggered?  Hardware triggers work extremely fast and can be driven off of either an internal or external clock.  Triggers are generally used when a hardware event occurs and something needs to happen at the next clock tick without delay or exception. You setup the task first and tell it that you don't want it to start until the trigger occurs.

Hopefully this is more along the idea of what you're looking for.  Let me know if you have any further questions!

[Vasilich2004]

>>Is the delay you're experiencing a product of the steps necessary to create the task?

No. This is delay when I give command start by DIO Start.vi . So this is internal delay of DIO Start.vi .

>>All of the VIs that are used to create a task and setup timing to require a small amount of processor time that you cannot reduce.

It doesn't take so much time.

>>Are you interested in setting up your task to be triggered?

No. I (try to) use module in next algorithm

- data acqusution - get data - calculation for PCI 6534 - load new data into PCI 6534

- software start and continuously play some times in pattern mode with external clock

Time "get data - calculation for PCI 6534 - load new data into PCI 6534 - software start" is critical and > 100 msec is unacceptable for system.

Also it was my mistake to put this message in LabVIEW board. I created another one in Digital IO http://forums.ni.com/ni/board/message?board.id=70&message.id=6400

Andrei.

[Elijah_K]

Hey Vasilich,

There's actually a great example using DAQmx that I think you should take a look at.  It acquires a digital signal when triggered in hardware.  The delay you're experiencing may not be unavoidable since it's up to windows to determine when a software process is excuted on the system.  By setting up the acquisition within the hardware, the task can be triggered without any time delays that windows might introduce.  This will be the most precise way in which you can control the timing of when the acquisition starts.