Has anybody used PCI-6561 for more than 10sec?

[pawel]

Hi All

Has anybody used NI PCI-6561 Digital Wfm, 100 MHz, LVDS, 16 Mbit/chan, for a continuous acquisition at 100MHz?

the other question:

How this board will cope with external clock at 80MHz? Any observations?

Thanks in advance

Pawle

[Allen H]

Hi Pawel,

On how many channels are you acquiring data?  If greater than 8, then you won't be able to acquire data continuously for 10 seconds because every sample is 2 bytes wide.  2 bytes at 100 MSamples/s is 200 MB/s, which is greater than the theoretical maximum bandwidth of the PCI bus (133 MB/s).

If you are acquiring 8 channels or fewer, then you only need 100 MB/s of bandwidth.  What do you need to do with your data?  Acquire it to disk, perform analysis, etc?  100 MB/s may or may not be possible depending on what you would like to do.

As for your other question, as long as your external 80 MHz has a duty cycle of 40% to 60% and otherwise meets the voltage requirements of the clock line you choose (CLK IN SMB or STROBE), then the 6561 will perform well.

I hope that helps,

Allen

[pawel]

Hi Allen

I need to acquire LVDS one serial signal at 80Mb/s. So I will use only one pair of lines, or whatever is needed for LVDS. Which means that I will need only 80mb/s which is 10MB/s. I shall be then in a very safe are, i.e. much lower than 133MB/s.

I need to do a thorough processing on those data, so I can not spare any of the processor recources for that.

Thanks a lot

cheers

Pawel

[JKnMI]

Pawel,

Your application is well within spec. You shouldn't have any problems.

Let us know if you have any further questions.


Regards,

Jessica Kinnevan
Applications Engineering

[Allen H]

Hi Pawel,

You are of course correct about the pure amount of data.  However, the 6561 is designed to capture samples that are either 1 or 2 bytes wide.  If you are acquiring on 8 channels or fewer, then you may configure your sample width to be 1 byte (8 bits).  Even if you are only acquiring on 1 single channel, the amount of data that is passed into the onboard memory and to the PC will be 8 bits for every sample.

It may be possible to add some external circuitry and deserialize the data stream before it reaches the HSDIO module.  Might this be an option for you?

Allen

[pawel]

Hi Allen

Ups... That is very important information, which you are telling me right now.

Lets see, 8b*80MHz = 80MB/s transfer rate.

I wanted to buy 16Mb/chnl, which basically means that at 80MHz I can store only 200ms as a buffer for PCI transfer. You said that the maximum transfer for PCI is much lower than 133MB/s. Is much lower means 80MB/s? 

Hmmm...  I need to think about it again.

Thanks a lot Allen

cheers

Pawel

[pawel]

Hi again

I forgot to answer for your question.

The serializing is not possible in this application. There is too much dependence on the actual clock (which is supplied to HSDIO modul from our board).

take care

Pawel