How can I reach ≥200KHz sample rate in digital io read(for port or more than one line)

[xhsun826]

I need to read two signals: one clock & one data.I need 200KHz to read them. 

first I use AI to read it (ai0 & ai1). if I read one signal one time, the sample rate can reach 250KHz. when I want to read two simultaneity, the sample rate go halves : only 125KHz.so I can read the signals availability.

second, I use digital io to read it. I want to use "DAQ Timing.vi" to improve the digital io sample rate. but i failed.

How should I do? and it is possible for PCI 6224?

i used the PCI6224 and PCI 6509 for the same project.

[QinFang]

Since the DIO module of 6224 doesn't have seperated clock, it can only be hardware timed(MAX 1M) through correlated DIO, you can refer to the following link for information

http://zone.ni.com/devzone/cda/epd/p/id/1566

[Neil_S.]

Can you provide a few more details?  With the 6224 you can read the DIO lines at higher rates by using a counter to generate the sample clock.  There are several examples in both C and LabVIEW that show how to accomplish this. 

Are there any analog signals that you are trying to read? If you are only reading digital signals I would recommend sticking with the digital lines to read these signals.  If you have more than one analog signal you cannot acquire them at higher than 250 kSs aggregate.  This means that the max sampling rate for any give analog input task is the max sampling rate (250 kSs) divided by the number of channels in the task.

Hopefully this give some idea of where to start, but if we had a better idea of all the signals you were trying to measure we might be able to make some better recommendations.

Regards,

Neil S.

DAQ Product Support Engineer

National Instruments

[xhsun826]

thanks ,Neil S.

just as you said, it's OK.

Frank-Fang , thank you .the link is useful