What is the RTSI device limit?

[CCITest]

I am in a little bit of a bind, and I hope one of you guys/gals can help me out.  Another engineer at our company spec'd a system that contains 7 PCI based cards (6552 HS-DIO cards) and he didn't realize that NI only sells RTSI cables up to 5 positions.  

My question is this:  is there a physical limit of 5 boards on a cable, or is it as this thread suggests, 8?

http://forums.ni.com/ni/board/message?board.id=250&message.id=1052

Reason I ask is I put a 7 position cable together (although only two were hooked up) and the Synchronize call into TClk was throwing errors.  As soon as I replaced the cable with a 2 position one, the errors went away.  I suppose it's possible that it's a poorly constructed cable, but I'd be happier to hear that it'll work once I hook 7 devices up.

Thanks!

-Mike

[sailor_12]

CCITest, 

It sounds like you know this by now, but National Instruments makes RTSI bus cables to connect up to only five DAQ devices. Probably because most desktop computers only have five internal PCI slots. However, the RTSI bus was originally designed to support up to eight cabled devices.

Since there is not an off-the-shelf RTSI bus cable to connect more than five devices, you will have to make your own custom RTSI cable. You could splice 2 of RTSI cables together to give a maximum of 8 connectors, or you could make your own from scratch.

You could use the following items to make one from scratch:

Inner Connector 3M Part# 3414-6000

Outer (closed end) Connector Part# 3414-7000

Cable - Any standard 34 Pin ribbon.

I would make sure you get enough cable to be able to reach between all of the RTSI connects. Hope this helps!

[Keith.Shapiro]

Mike -

Something to keep in mind is that (from your other thread) you were only using 2 devices with a 7-port cable.  You might have better signal integrity if all of the ports were hooked up and properly terminated.

Best of luck,

Keith Shapiro

National Instruments R&D