Reflection problems with PCI-6534 at 15MHz using screw terminal block.

[cmoffa01]

Problem: Receiving significant distortion on high-speed data and clock signals due to reflections and impedance mismatches.

Setup: 15MHz output from cmos logic chip into NI SCB-68 Shielded Connector Block, then through 2 meter
SH68-68-EP Shielded Cable to PCI-6534

Question: What is the impedance of the cable, connector block, and input to the 6534? Can I get a copy of the 6534 interface schematic so that I know what my signals are going into? The data sheets for the connectors and cables on the NI web site do not have any characteristic information. Are there any detailed data sheets? Does NI have a solution to get my low current high-speed signals into the 6534?

[June]

Hello:
This web knowledgebase offers some specification for the SH6868-EP cable: http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/36220e8f02bf21288625686900766e27?OpenDocument
However, for 653x applications, it is recommended for users to use the SH 6868 D1 cable. The D1 cable is optimized for digital and counter boards. Please see the following knowledgbase with more information on this topic as well as input and output impedance of the 653x devices: http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/783d15b155fac6f1862566b3006a32f0?OpenDocument
Aside from switching to using the correct cable, you may want to consider decrease the length of the cable if your application allows that. National Instruments offers SH 6868 D1 cable
in various lengths, 0.5m, 1m, or 2m.

Regards,
June