Maximum Frequency of RTSI Cables

Updated Oct 6, 2018

Reported In

Hardware

  • RTSI Cable
  • PXI Chassis

Issue Details

I have a PCI-based data acquisition board and I want to send a high frequency signal across the RTSI bus. In this particular application, I am trying to send out a 20 MHz reference clock so that I can phase-lock-loop (PLL) two PCI boards. But, when I try to send the clock across the RTSI bus, the frequency remains the same, but I am getting the wrong duty cycle (30% or 70%, instead of 50%). What is the maximum frequency that I can send through the RTSI cable?

Solution

There is no formal specification as to what is the maximum frequency that can be sent through the RTSI cable. With PXI-based instruments, the PXI trigger bus lines are rated at 20 MHz, which is part of the PXI specification. There is no such standard for PCI. The highest stable frequency that can be attained is around 10 MHz. Going beyond this value will start to distort the signal's duty cycle. It is possible to send higher frequencies, but this is based entirely on what type of cable you are using and also what your allowable tolerance is for the signal's duty cycle.

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