Compatibility Between PXIe-8431 and VHDCI Flying Leads Cable

Issue Details

I am exploring options to break out the VHDCI port of my PXIe-8431/x serial interface device into bare cables I can connect directly to. I found out NI has the SHC68-H1X38 cable, which has flying leads at one end of the cable and a VHDCI connector at the other. Can I connect this cable to the VHDCI port of my PXIe-8341/x given the cable also has VHDCI capabilities?

Solution

The PXIe-8431/8 and PXIe-8431/16 devices are a high-performance interface for high-speed communication with RS485 and RS422 devices. Even though these devices have a VHDCI port in their front panel, and that the cable can fit into that port, the cable was not designed for the same application as the serial devices. Therefore, the electronic circuitry behind the port won't match the characteristics of the the SHC68-H1X38 cable.

For example, the SHC68-H1X38 cable has a 50 Ω impedance because this cable is design to operate with high-speed digital cards. Nevertheless, serial communication devices usually operate at impedances of 120 Ω. The PXIe-8431/8 and the PXIe-8431/16 include a 68VHDCI-DB9M Serial Cable, part number 197546-01, for RS-485 standard communication. The recommended approach is to use this shipping cable and connect it to a 3rd party DB9 break out board.