digital IO speed

[wejc]

I am interested in using Labview to tell a Delta Sigma converter to convert at a 1 Khz rate, ie sending a 'convert' signal every millisecond and then receiving the 20 bits of serial data with receipt of a 'conversion done' signal....do I need the Labview RT tool to do this or can the digital IO of a PCI6023E keep up with such a data rate....or utilization of a computer LPT port or ??

[rgharrison]

Hi wejc,

If you need a digital signal to be output at a 1kHz rate then it will be very difficult to time using the PCI-6023E and Windows. The main reason is that the digital I/O on the 6023E are not timed or clocked. They are asynchronously controlled by a software call. Therefore you would need to setup a software loop to constantly update the digital lines. From my experience, I have found it difficult using any Windows OS and a 1GHz machine to have my loop execute at least once per ms. This means you will probably need a different solution. Here are the options I am thinking about:

1) As you mentionned, a real-time system would do the trick. This would require LabVIEW Real-Time and an E Series card with an embedded controller for the real-time
application. This would work because you can now achieve predictable timing at sub-ms times. However...

2) I believe a more economical solution would be to get a synchronous digital board such as the PCI-6533 (PCI-DIO-32HS). This board is capable of outputting data on a stable clock which can be configured for 1kHz. This board can go much higher in speed as well.

Anyway, I hope that helps.

Ron
Applications Engineer
National Instruments