synchronicity between cards (PCI-6541)

[Harpoon]

I have two PCI-6541 cards which I am using to control two different digital interfaces to my device. The one thing these interfaces share is a single clock, so I need to synchronize both cards. What is the recommended way of doing this? Connecting the clock in of one card to the clock out of the other card, and selecting clock in as the reference on the 2nd card?

[Allen H]

Hi Harpoon,

What sample clock frequency do you need?

The 6541 is one of our SMC-based devices, which means it has our NI-TClk synchronization technology. Using NI-TClk, you can easily synchronize multiple boards. If you have already installed the NI-HSDIO driver, then you can take a look at a few example programs that ship with the software. If you are using LabVIEW, open the example finder (Help --> Find Examples), then go to Hardware Input and Output --> Modular Instruments --> NI-HSDIO. Depending on whether you are doing Acquisition, Generation, or both, you can pull look in the appropriate folder and find a "Multi-Device ... (TClk)" example.

To download NI-HSDIO, go to ni.com/download, then click on Driver and Updates --> Current Software Versions --> Digital I/O --> NI-HSDIO version 1.3

With NI-TClk, the sample clocks of the two boards will be synchronized to within 1 ns or better. Also, since you are using PCI, you will need a RTSI cable to use TClk.

I hope that helps get you started.
Allen

[Harpoon]

Hi Allen-

Thanks for responding.

We are running two interfaces on these boards; one is a microprocessor-like interface (8 bit data, 6 bit address & some control lines) so that's generation and acquisition on this interface, and a burst data bus which is 8 bits of data & some control (generation only). We coded up both of these interfaces for the one board we have installed now, and they work but not at the same time. 🙂

The clock speed on these two interfaces is a relatively leisurely 33 MHz.

Where does one acquire an RTSI cable?

Mark

[Allen H]

Hi Mark,

So you will have a total of three sessions (two generation and one acquisition) across two boards that I presume should all start at the same time. For this, I recommend the Multi-Device Dynamic Acquisition and Generation-Source Synchronous (TClk) example. The two generation sessions will be synchronized with TClk, and the acquisition session will start based on the data active event from the generation session.

You will need to make a slight modification to this and the other TClk examples when using a PCI board. TClk depends on a 10 MHz reference clock that is shared between all boards. In a PXI chassis, this 10 MHz clock is automatically present. For PCI, you must explicitly export the 10 MHz clock from one of your two 6541s. This is demonstrated in the Dynamic Generation with Reference Clock (PCI) example.

You can find more information about the RTSI cables from this web page:
http://sine.ni.com/nips/cds/view/p/lang/en/nid/4794

Allen

[Gil W]

Hi Allen -

I am in the same situation. I have two PCI 6541 cards. All the channels on one card are devoted to generation. The second card is split with 16 generation and 16 acquisition. I have a RTSI cable connecting the cards. I am trying to get all the generation and acquisition sync'ed. My case is simple because all devices are at the same sample rate. I can successfully use TClk to setup up both of the generation sessions. But I run into trouble when I add the acquisition session. The TClk functions don't like to have two sessions on the same card. When I try to follow the examples you suggest, the TClk_Initiate returns an error if I have initiated the Acquisition session:

Error -250034: NI_TClk initiated a session, and the instrument driver reported an error.

Also, the example you mentioned made use of external connections. I would like everything to work over the RTSI with no external clock or trigger connections if possible.

Thanks! Gil

[ryanm]

It looks like the last post was made in two locations.  Please go here to reply to Gil's post.

Thanks,

Ryan M.