Can I Use PCI6534/PXI6534 to generate different CLK 20MHz/10MHz or 16MHz/8MHz ?

[YJ2003]

I am using two DIO board(PCI6534) to test TWO kinds of Devices Under Test(DUT), DUT1&DUT2. The DUT1 need two Clock inputs (20MHz & 10MHz); DUT2 need two clocks (16MHz&8MHz).

So our requirements of signals generating are:
1. CLK2=20MHz,CLK1=10MHz (DUT1),
2. ClK2=16MHz,CLK1=8MHz (DUT2),
3. We can test DUT1&DUT2 seperately, however, ClK2 always has to have a frequency twice as high as CLK1.

According to the 653x manual, I suppose I could use the REQ (for 20MHz CLK2) and one digital channel(for 10MHz ClK1)to do the job.

My Questions are:
1. Could you give me some info about the duty cycle of REQ at 20MHz. As we prefer 50% for the CLK2? I monitored the REQ in my PCI6534 with scope(
60MHz), the output of REQ is badly contaminated at 20MHz while REQ shows a sine wave at 10MHz. Could you give me some advice on that?
2. Can I use PCI6534 to generate the 16MHz or 8MHz?
3. If not, can you recommend some other DIO boards to fulfil our requirements?
4. We are planning to buy another two PXI6534 for similar test purpose. So any better ways to generate the CLKs(20MHz&10MHz) by PXI6534?
5. Would PXI6551/2 solve our problem?

Thanks in advance. YJ2003

[YJ2003]

1. You can not use 6534 to generate CLK 16MHz/8MHz, because the frequency divisor has to be integer.
2. One possible solution is to use counter/timer 660x to generate a clock of 16MHz,20MHz and connect it to the REQ pin of 6534.
3. As for other questions, you would better post them again...

Have a nice day!

[PNHorn]

Hi YJ2003,

It's Peter H from National Instruments technical support department here. I have been asked to look into your problem. You are correct when you say that you can't get clock rates of 20 MHz and 16 MHz simultaneously from the 6534 card as this card has a max clock rate of 20 MHz, and the divisor has to be an exact integer. So you can get one or the other, but not both.

You asked if the PXI-6551/2 would solve your problem. The 6551 won't help as this has a max clock rate of 50 MHz, from which there is no exact number from which you can divide down to both 20 MHz and 16 MHz.

The 6552 should work OK though. This card has a max clock rate of 100 MHz. If you set the clock rate to 80 MHz then you can use a divisor of 4 to get to 20 MHz and
a divisor of 5 to get to 16 MHz. From both of these, you can obviously divide by 2 to get to 10 MHz and 8 MHz respectively.

Hope this helps, if you have any more problems, please respond to this post.

Best regards,

Peter H.
Applications Engineer.
National Instruments.

[YJ2003]

Hi Peter,

According to my understanding, I can NEVER get 16MHz CLK from 6534 itself as 6534 uses a 20MHz oscillator to generate the clock. So the only clock I can get from 6534 itself should be 20MHz,10MHz,6.667MHz...Am I correct?

[PNHorn]

Hi YJ2003,

It is possible to get a 16 MHz clock from the 6534. There are however some issues to be careful about though. I have pasted some links below which may be useful to you.

Benchmarks:
http://digital.ni.com/public.nsf/websearch/4FCA248D888831C386256D8900563E45?OpenDocument

Why is Burst Mode faster?:
http://digital.ni.com/public.nsf/websearch/23F9E5BE7B740C7086256CD70055095E?OpenDocument

Burst Mode Clocking:
http://digital.ni.com/public.nsf/websearch/862567530005F09C862566B1006F43AB?OpenDocument

Pattern I/O Clocking:
http://digital.ni.com/public.nsf/websearch/2FB93421FAD8374286256BDF007A78AF?OpenDocument

Basically, it should be possible to use a 16 mHz clock, but only in burst mode or pattern i/o mode, wit
h burst mode being much more reliable.

Best regards,

Peter H
Applications Engineer.
National Instruments.

[Allen H]

Just a quick correction on Peter's comments. The 6551 and 6552 both use a 200 MHz internal clock to derive the On Board clock frequencies. While this still will not allow you to reach 16 MHz, you may use 16.6 or 15.36 MHz.