How to use 20 MHz clock of the 6602 Timing card on other boards?

Question

Hello,
I have a 1042 PXI with 6602 timing card and several other boards including 6534 Digital I/O board and 5122 Digitizer.
I want these boards (6534 and 5122) to use the 20 MHz clock of the 6602 board as their Sample Clock.
But when I set "/TimingIO/20MHzTimebase" as the source of the Sample Clock for the 6534 board I get the following error sometimes (sometimes everything works fine) :
"""Error -200621 occurred at DAQmx Wait Until Done.vi:2
Onboard device memory underflow. Because of system and/or bus-bandwidth limitations, the driver could not write data to the device fast enough to keep up with the device output rate. Reduce your sample rate, or reduce the number of programs your computer is executing concurrently. """
When I use "OnboardClock" as the source of the Sample Clock for 6534 I never get this message. I tell 6534 to use 6602's 20 MHZ clock by connecting
"/TimingIO/20MHzTimebase" terminal to the appropriate input of the
"Sample Clock vi" in the 6534's task. Output rate of the 6534 that I use is (much) less than 1 MHz.
Could somebody explain the source/reason of the error message above? It seems like 6534 can not use 6602's 20 MHz clock though it has 20 MHz oscillator itself...
Is there a way to use 20 MHz clock of the 6602 for 6534?
Thanks in advance!

Answer 1

Hi Ampm,
The two answers are related to each of the answers:
1) In this knowledgebase we can see that actually the 6602 cannot
export his clock into PXI_Star. Since your digitizer cannot received but from
this line, we need to find a different solution (see below).
2) PXI_Star is actually a signal and should be named something
like this “/Slot5/PXI_Star”. Make sure you PXI chassis is configured in MAX.
There are two possible approaches:
1)     
I would suggest to PLL all
clocks to the PXI 10 MHz clock. This takes full advantage of the hardware you
have.
2)     
Export the 6602 20 MHz clock
on a front panel PFI line and externally connect it to the CLK IN of the 5122.
Good luck,
Gerardo O.
RF Systems Engineering
National Instruments