can PXI 6552 change the frequency on the fly?

[AhGang]

Hi,

    Can PXI 6552 change the frequency on the fly during pattern running?

    If yes, how long will it take to change?

    Thanks,

    AhGang

[Ryan_M]

AhGang,

No, you must stop the session in order to change the frequency.   However, if you know when you want frequencies to change, you can use data repitition to effectively change the frequency.  That is, if you want to generate a pattern:

010101010101010

and change from 50MHz to 25MHz half way through you can create a waveform that looks like

0101010100110011001100

if you need a source synchronous clock then you can set the board up for 100MHz and create a clock on an alternate date line

"clock"  01010101010101010011001100110011001100110011
"data"   00110011001100110000111100001111000011110000

The hardware has to be running at a constant frequency but you can make the data look like other frequencies by using this data repitition strategy.

[AhGang]

Hi Ryan,

    This solution can only work for 50Mhz and 25Mhz. It may have trouble for 40Mhz and 20Mhz.

    I plan to use an external clock source such as PXI 5406. But some considerations are needed:

    1. When the pattern is gonna to change the frequency, PXI 6552 will send out a event as a trigger to PXI 5406. This is to inform PXI 5406. I think this shall have no problem. right?

    2. Sending trigger to PXI 5406 can be very fast. But how fast is it for PXI 5406 from receiving the trigger to the time the new frequency is stable? This can be done by hardware or need software?

    I am not sure if NI ever did this experiment or not.

    Thanks and regards,

    AhGang