USB-6501 has no I/O Timing?

[donpettengill]

I am evaluating this device for some computer-controlled I/O needs, but it looks like the USB-6501 has no I/O timing? The data sheet says max input frequency 5 MHz, but I see in the knowledge base real input rates of 1 Kbit or less, untimed. Actual transfer rates will be far less, since the timing has to be software controlled and so data has to be sent *one bit at a time* with a software handshake. Some preliminary tests on our part show real data rates maybe a few to several tens of bits per second, if we're lucky. I suppose the same goes for data output, although here at least we can generate a clock to go with the data, so maybe we'll get a few hundred bits/s.

This wasn't at all the impression I had from the datasheet. I was thinking more along the lines of abs max clock rate 5 MHz, ie a data rate of 1 Mbit should be fine.

1) Is this reallly true - a digital I/O device with no incoming or outgoing data latches?

2) Is there another NI product that can do sensible clocked digital I/O? 8 bits at 1 MHz is plenty. After this experience with the USB-6501, I don't want to rely on the datasheet to see what might be suitable.

Thanks!

Don Pettengill

[Dennis_Knutson]

You must have been looking at the wrong data sheet or maybe you were reading the section on the counter. The specs listed here and in the pdf data sheet referenced there, clearly state that the digital I/O is software timed. A great number of applications only require static digital I/O (like the work I do) and it's perfectly suitable for those applications. Yuo might want to look at the M Series device which have hardware timed digital I/O (up to 1 Mhz).