Generate PXI Trigger Signals with PXI-6115

Question

Hello,
I have a question.
I have a PXI-6115 and some other card in my mainframe.
These other cards nee 10 Mhz pulses on line PXI-Star1 and 2.5 MHz on PXI_trg7.
So I thought to apply (somewhere on my PXI 6115 card) 10 MHz, divide the 10 MHz with a counter to 4 and route all this things to the backplane.
But I don't understand how to do this.
There are no good examples.
And as far as I know the PXI-6115 isn't yet supported by DAQ-MX.
Can anybody give me some good advises or tips, white paper or so to make me solve my problem ???
Thanks Ruediger

Answer 1

I don't have time to write any example snippets right now, but I'll try to provide you the general idea and hopefully you can take it from there.
First, it's not clear whether you want to generate the 10 MHz from the 6115 and send it to other devices in the system or accept the 10 MHz externally and route it to the rest of the system.  If you're bringing in the signal externally, I would simply using the DAQmx Connect Terminals VI to route the signal from a PFI line on the front connector of the board to one of the PXI trigger bus lines in the backplane.  Check out the routing table in MAX to see what routes are possible.  To perform this route, the driver will have to route through Counter 0 so you won't be able to use Counter 0 for anything else.
If you want to generate 10 MHz from the 6115, I would create a continuous pulse train task on Counter 0 using the CO Pulse Ticks version of the Create Channel VI with a value of 2 for both the high ticks and low ticks input.  However, to achieve 10 MHz clock on a PXI trigger line, you'll have to perform a couple of modifications that typically aren't done with counter tasks.  First, you'll need to use the DAQmx Export Signal Property Node to route the Counter Output Event to the desired PXI trigger line.  You can find this property by navigating the following menu hierarchy Events->Counter Output Event->Output Terminal.  By default, the driver routes this event to the Ctr0Output pin on the front connector of the board.  Using this property will override this behavior and route the output of the counter to a PXI trigger line instead.  Second, you will need to change the output behavior of the Counter Output Event from toggle to pulse.  This can be through the Events->Counter Output Event->Output Behavior property.  Normally, when generating pulse trains, the high ticks and low ticks parameters from the Create Channel VI determine the frequency and duty cycle of the pulse train.  When the high ticks count expires, the output of the counter toggles.  The low ticks value is then loaded into the counter, and the counter output toggles again when the low ticks value expires.  This process repeats to produce a pulse train of the desired frequency and duty cycle.  Since the counter uses a 20 MHz timebase and has a minimum low ticks and high ticks value of 2, you can only produce at maximum a 5 MHz pulse train using the toggle behavior.  However, by changing the output behavior from toggle to pulse, the counter output will issue a short pulse each time the high ticks and low ticks counts expire yielding a 10 MHz clock signal.
Now that you have the 10 MHz signal taken care of, you need to generate a 2.5 MHz signal from it.  My guess is that since you have a 6115, you already have plans for the AI engine so I'll describe a route that uses AO instead.  First, create an AO task to perform continous waveform generation.  Use the DAQmx Channel Property Node and set the Use Only Onboard Memory property to true.  Setting this to true will cause the driver to download the waveform once upon starting the task and replay the waveform from the onboard FIFO.  Since you're only using this task to generate a clock, you don't really care about the data and this will prevent unneccessary traffic across the PCI bus.  Next, use the DAQmx Timing Property Node to set the Sample Clock->Timebase->Source to the PXI Trigger line that you're generating the 10 MHz clock on, and set the Sample Clock->Timebase Divisor to 4 (10 MHz / 4 should give you a 2.5 MHz sample clock).  Last, use the DAQmx Export Signal Property Node to set the Clocks->Sample Clock->Output Terminal to the PXI Trigger Line you want to generate the 2.5 MHz signal on.
It requires some creative programming, but you should now have a 10 MHz and 2.5 MHz signal routed onto two different PXI Trigger lines.  I know this solution is a bit involved so if you have any further questions be sure to post back.