PCIe-6536 question

[acct5]

I am considering using a PCIe-6536 (or 6537) digital I/O board for a project.  I've read the spec sheet and I think it will work but I wanted to get some advice first before I spend the time and money on this.

The 6536 has four 8-bit ports.  I want to write out 8-bit data on Port 0 and simultaneously read in 24-bit data on Ports 1-3.  The data written out will be in a huge array of several hundred megabytes.  The data read in will be stored to an array of the same size except it will be filled with 24-bit words. 

I want to use a single external clock source for the simultaneous reading and writing and it will be a 15MHz clock.  The code to do this will be in Visual C++.

Anybody see any problems with this idea?  Any advice on things I should watch out for?

Thanks for any help.

[Greg-H]

Hi,

Both devices are going to have the 8-bit output ports and the 24-bit input ports.  The 25Mhz on the PCIe-6536 is plenty for the 15MHz external clock.  The 6 PFI lines are in addition to the 32 digital I/O channels so you will have a way to reference your external clock.  Although the PCIe-6536 has an on board clock as well.  I think the PCIe-6536 is fine for your application, the only reason I can see getting the PCIe-6537 instead is if you plane on expanding your application later on.

One issue you may have is the execution speed of your digital reads and writes if you plan on doing a lot of data manipulation.  If you are going to be doing intensive data manipulation I would use a producer/consumer loop set up so that your digital reads and writes are not slowed down.

Regards,

Greg H. 

[acct5]

I don't need to do any data manipulation.  Just need to write 8 bits out and simultaneously read in 24 bits, using the same PFI clock pin.  The amount of data to write and read is fixed.  For example I may write out 200 million bytes and read in 200 million 24-bit words.  (After the data is read in, then I will do processing on it.)

Can I use PFI 4 for the external clock input?

Thanks.

[Greg-H]

Hi,

The manual says "3 bidirectional clock terminals (PFI 4, PFI 5, RTSI 7)", so yes you can use PFI 4.

Regards,

Greg H

[acct5]

The manual does say that but I can't find anywhere in the manual that specifically says that I can use a single PFI pin to *both read in and write out* at the same time.  I guess I'll try it and see if it works...

[Greg-H]

Hi,

You won't be able to read and write on the same PFI line unless you clear and recreate the task every time you switch from read to write or vice versa.  This device has several PFI lines so you could just use one as read and another for write.

Regards,

Greg H.