rsti cable construction

[lindope]

Can I make an RSTI cable for linking two boards using two 34 pin ribbon connectors and some ribbon cable? Or is there something special about the cables I would buy from NI? i.e. are they one-for-one pins? or are there a few unconnected/open?

Christopher

[Kevin_Price]

Unofficial answer: in a pinch, I have done this with success using straight one-for-one connections.  I'm not a cabling expert though, so there may be some compromises with digital signal integrity, especially for very high freq signals.  The signals I routed over RTSI were likely in the range of 10's of kHz or lower, and I had no problems at all.

-Kevin P.

[John_P1]

Hi Christopher,

The RTSI connectors use a standard 34-pin ribbon cable with straight-through connections so you should be able to make your own cable if you want to. 

One thing to add is that we can't guarantee the integrity of any signals coming over a custom cable (like Kevin said, higher frequencies might start to give problems).

Best Regards,

Message Edited by John P on 01-26-2010 11:49 AM

[lindope]

I found an old 34 pin floppy disk drive cable, cut one end off and pressed one of the other connectors to the short ( 2") piece. I verified continuity on all 34 pins, I verified no shorts from adjacent pins.

I connected the 2 PCI 6251 boards using this cable. I ran MAX and clicked one of the boards and chose "Properties"

There is a window that shows RSTI connection and both cards show "None" in the pull down menu with no other selection possible. Does this mean it's not working?

Is this the correct way to tell if it is working? or is there a better way to verify shared sample clock?

[lindope]

I noticed in the M Series Manual (page 9-5) there is a connection chart. I believe it gives these as reference for connecting the RSTI bus to external signals/sources.

The chart says pins 1-18 "Not connected. Do not connect signals to these terminals."

I'm assuming this is a warning for external signals? and not from card to card?

[John_P1 · Accepted solution]

Hi lindope,

Whether you're using an NI supplied RTSI cable or a self-built one, you will still need to configure the cable in MAX.  The following link shows more information on how to do this:

What is RTSI and How is it Configured?

The "Not Connected" indication in the manual is just telling you that we do not use these lines on our cards.  In fact, we only use 8 of the 34 lines for actual signal routing.  The remaining lines are either not connected or are connected to digital ground.

Best Regards,

[lindope]

That worked! Thanks.