What type of termination resistors should be used for ACC-LON or FTT-10A remote I/O modules.

Issue

Wants to know the correct termination specification for each different I/O modules and different IOU networks.

Product Line

Andover Continuum

Environment

  • NC1 - CX9900, CX9940
  • NC2 - CX9680
  • IOU modules

Cause

Different type of terminations are required for different type of I/O modules (ACC-LON and FTT-10A) and different topologies (Bus topology, Free topology and Doubly terminated Bus topology).

Resolution

  1. ACC-LON  requires two 120 ohm resistors at both ends of the bus. One between pin 1&2 of the I/O module on the NetController side and the other one between pin 1&2 of the I/O module at the last node of the bus.
  2. FTT-10A Free topology requires one 52.3 ohm resistor between pin 1&2 at any place on the bus.
  3. FTT-10A Doubly terminated bus topology requires two 105 ohm resistors.  One between pin 1&2 of the I/O module on the NetController side and the other one between pin 1&2 of the I/O module at the last node of the bus.