Re Triggering Using PCI 6534 and PCI 6602

[057768022]

Hi,

I am using the PCI 6534 group A (LABVIEW 8.2, DACmx ) to generate data words (Each word ~ 47000 bits, ~14msec) using external CLK (4.2 MHz). I am using group B to receive data words using external CLK.

The words are generated with periodic external trigger pulse (~17 Hz). (The time between two triggers is ~ 42 msec)

Sometimes words aren't written correctly. (Missing the external trigger?)

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

I under stood that I can solve this issue using PCI 6602 counter. (The external trigger will Re trigger the PCI 6602. The PCI 6602

will initiate the PCI 6534 via RTSI cable.

I would like to ask,

1. Is there a special line in the PCI 6534 for the RTSI input from the PCI 6602?

( I hope that I don't need to use the external CLK line, because it is occupied)

2. Using the above rates, is it possible to generate one word upon each trigger?

3. What are the limitations of such system, in term of external trigger rate?

4. Will it solve my missing data generated words?

I would like to receive a full "picture" of this system (HW/SW) before ordering PCI 6602.

Thank you for your information.

Best Regards,

Nir

[Daniel_L]

Hi Nir,

That's an interesting question that you have here, so let me see if I understand your application correctly.  But first, let me answer some of the questions first:

1. Is there a special line in the PCI 6534 for the RTSI input from the PCI 6602? (I hope that I don't need to use the external CLK line, because it is occupied)

• No, the RTSI cable does not need to use the external CLK line.  There are 7 different RTSI lines that you can use that are universal to the RTSI bus. 

2. Using the above rates, is it possible to generate one word upon each trigger?

3. What are the limitations of such system, in term of external trigger rate?

4. Will it solve my missing data generated words?

• I did some of the calculations, and the numbers didn't seem to add up.  Could you recheck your numbers, or perhaps draw a simple timing diagram?  I also want to make sure that the 6602 is the right card for you before recommending it. 

Thanks,

Daniel L.
Applications Engineer
National Instruments

[057768022]

Hi Daniel,

I added my data generation timing diagram.

My first task was to transmit one data slot. (Each run, only one slot was generated based on external trigger)

I used DAQmx trigger function. (I have noticed that even in that mode (Using scope) that sometimes (one out of 50) the slot wasn't generated correctly.

That application run quite well.

-----------------------------------------------------------------------------------------------------------------------------------------

My second task was to transmit one data slot, upon each periodic external trigger.

In order to do that, i modified my LABVIEW file to include a while loop.

Using that method I saw that ~20 % of data slots weren't transmitted correctly.

I hope that you managed to get a better picture of my data generation problem.

-------------------------------------------------------------------------------------------------------------------------------------------

From your response I understand that I can apply my external trigger to PCI 6602, and stay with my external CLK connected to 

PCI 6534.

If the PCI 6602 is a possible solution, please descfribe in details (HW connections / SW LABIEW) your suggestion. 

Best Regards,

Nir Corse  

[Daniel_L]

Hi Nir,

Thanks for the timing diagram; I see what you are trying to do now.  Here are my thoughts:

It sounds like you would like to configure the 653x device to re-trigger.  However, re-triggering is not supported by the 653x hardware.  You basically have two options from this point, and I think that you've already tried option 1: 

Option 1:
Reconfigure the device and wait for the new trigger(s). However, reconfiguring takes time, so this option will not work if the application has very tight time constraints.

Option 2:
Configure the 653x device for a pattern input (or output) operation, and use a counter to generate the clock signal.  One method would be to use a 660x board to generate the clock signal.  We have an example already written with the hardware and software description for Continuous Pattern Output with Retrigger.  This example is written in Traditional DAQ; what version of LabVIEW and DAQ are you using? 

I hope this helps shed some light on your application. 

Daniel L.
Applications Engineer
National Instruments

[057768022]

Hi daniel,

Thank you for your replay.

We have tried option 1. (Doesn't work)

We are using LABVIEW 8.2 (DAQmx Drivers) and Windows XP.

------------------------------------------------------------------------------------------------------------

1. Your option 2 is not clear. What clock should the PCI 6602 generate? (Is it the pattern signal to the PCI 6534 upon each external trigger to the PCI 6602?)

2. Doe's the PCI 6602 will be connected via RTSI? (To what line in Group A?)

Best Regards,

Nir

[057768022]

Hi Daniel,

I think that the following will solve my problem,

1. The external trigger will be connected to the PCI 6602.

2. The PCI 6602 will initiate a CLK to the PCI 6534 (REQ).

3. Upon each external trigger 58800 CLK bits will be generated.

Is it possible to modify the PCI 6534 data pattern?. (Data slot 1 is different than data slot 2)

Best Regards,

Nir

[Daniel_L]

Hi Nir,

You can use the "Regeneration" property node to disallow regeneration.  With the NI 6534, if you want to repeatedly regenerate the same block of data, you can load a buffer of data into onboard memory and continuously loop through this data block. With this option, data is transferred from computer memory to the NI 6534 onboard memory only once, and the device generates the same block of data continuously from its onboard memory, allowing the device to generate data at higher rates because it is not limited by the PCI bus bandwidth. Use the Use Only Onboard Memory property/attribute to enable onboard memory looping.

This should work in theory, though you might want to check the sample rates.  Would you like to send me your code and have me try out your generation program for the 6534 with the 6602 before actually making the purchase?  Either I or one of the other AE's could probably test it out for you really quick. 

Regards,

Daniel L.

Applications Engineer

National Instruments

[057768022]

Hi Daniel,

I can't send you my data generation code due to my restrictions. ( I also don't think that in will contribute here)

My suggestion is,

1. Generate 2 different random bits vectors of 53900 bits each.

2. Configure the *.vi to PCI 6602 and PCI 6534 data generation.

3. Connect the external trigger to the PCI 6602.

4. Set the "do not allow regeneration" property and try to load  each external trigger the on board memory

with a different vector.

5. You can check if the transmitted data slots are transmitted each trigger, and if you manage to peak a different vector each time.

----------------------------------------------------------------------------------------------------------------------------------------------------------------------

- Please let me know if what I wrote in my previous reply, regarding the description of connecting the PCI 6602 and PCI 6534 is correct.

Thank you for your help,

Nir

[Travis G.]

Hello Nir,

The NI-6602 is a counter/timer device capable of generating hardware retriggerable pulse trains, triggered off of an external digital signal.  Hardware retriggerable means that the counters on this device can quickly rearm and wait for a new trigger signal, without any software or driver calls.  From your application, it sounds like you should use the NI-6602 to generate these retriggered finite pulse trains, and use these pulse trains as a clock signal for the NI-6534. 

Using the output of a pulse generating counter as the sample clock source on another device can easily be accomplished using the RTSI bus on each device.  Using RTSI lines to transfer timing and triggering signals between devices does not require any external connections besides connecting the two devices together with a RTSI cable.  You then specify in your program for the counters on the NI-6602 to be output on a specific RTSI line, and then use that same RTSI line as the Sample Clock source on your NI-6534.  To verify that these device routes are available, take a look at the Device Routes tab for each device under Devices and Interfaces > NI-DAQmx Devices (simulate the devices if you don't have them in your system).  Notice that a direct route exists on the NI-6602 between the Ctr0InternalOutput (the output of counter 0) and all of the RTSI lines on the device.  Also on the NI-6534, that a direct route exists between all RTSI lines and the Dig0/SampleClock (digital sample clock 0).  Therefore, all you need to do to transfer the counter output of the NI-6602 to the sample clock of the NI-6534 is to create a RTSI cable in MAX and add both devices to it.  Then within your program, specify the Ctr0InternalOutput on the PCI-6602 as the sample clock source for your generation task with the NI-6534.  The DAQmx driver will take care of all the signal routing for you.



I hope this helps to explain how RTSI lines can be used to transfer timing and triggering signals between devices, and let us know if you have any further questions.

Regards,
Travis G.
Applications Engineering
National Instruments
www.ni.com/support

Message Edited by Travis G. on 10-30-2006 10:49 AM

[057768022]

Hi Travis,

Thank you for your reply.

I have the PCI 6602 and I will set it.

I would like to ask the following:

1. From your description I understand that you are using the PCI 6602 in order to generate triggered CLK which will be used to sample CLK the PCI 6534.

I added my timing diagram in my previous replays. I already have this triggered CLK from an external device. I am entering it as external CLK in my data generation. (I don't see the difference)

2. If I am using the PCI 6602 to generate the triggered CLK. How the PCI 6534 will reset  upon each trigger. (The trigger to the PCI 6602)

Because I need the data from the start upon each trigger.

3. Can we speak by phone? If yes please send me your number and hour.

Best Regards,

Nir Corse