6674T clock distrubution via DStarA with 4 7966 FlexRIO modules in a PXIe-1082 rack fails

[vlipje]

I'm trying to distribute a clock generated with a NI-PXI6674T timing and control board to 4x NI-PXI flexrio boards. I'm using DStarA to distribute the clock. For some reason the clock is only received by slots 2 and 3 in my NI PXIe-1082 rack. The other slots 5 and 6 do not receive the signal since the code won't run on Flexrio boards mounted in slots 5 and 6. The 6674T is mounted in slot 4. I try to understand why it will not run, I probably missed something in the manuals.

 

The DDS oscillator on the 6674T board is set at 50 MHz clock. This signal is routed to the DStarA lines of the chassis.

The FPGA code will only run on PXI7966 flexrio modules mounted in slot 2 and 3. Running the code on modules mounted in slot 5 and 6 fails.

[TylerK]

Hi,

I hope the following helps.

Short answer
On the PXIe-6674T, you should connect DDS Clock to PXIe_DStarA[1,2,8,9] (requires 4 separate routes)

Long answer
With the PXIe-1082, PXIe_DSTAR2 connects to slot 2, PXIe_DSTAR1 connects to slot3, etc. (For more details on PXIe_DSTAR connections, refer to the connectivity diagram in the System Timing Slot section of the PXIe-1082 User Manual)  Also, the PXIe-6674T routes to PXIe_DStarA in banks (groups of lines). That being said, there is a side effect of connecting DDS Clock to PXIe_DSTARA0; DDS Clock is also connected to PXIe_DSTARA[1..3]. This is why slots 2 and 3 receive the clock generated by the PXIe-6674T but slots 5 and 6 do not receive the clock.  It is best not to rely on this behavior and make the explicit connections you need.  The user manual for the PXIe-6674T describes how the PXIe_DSTARA lines are grouped (see the PXIe_DSTARA Network section).

Additional Comments
Routes on the PXIe-6674T are unaffected by closing the NI-Sync session.  It is usually best practice to disconnect all routes before closing the session.

Useful Link
PXIe-1082 User Manual
PXIe-6674T User Manual

Regards,
-Tyler

[vlipje]

This helped me a lot. Got it running now, great. Still puzzles me why DStarA1..3 all connect to slots 2 and 3 and the same for DStarA8..11 to slots 5 and 6. It's not just one line, but anyway, I'll stick to the proposed setup as described in the manual.

Thanks a lot!