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The CNOS-101 is a serial port expansion module for Schneider Automation's TSX Compact PLC. The module gives the Compact two additional serial ports that are switch-selectable RS-232 or RS-485. The CNOS-101 includes an LCD screen and 5-button keypad which simplifies basic configuration such as setting the serial port mode and baud rate. The LCD also provides the ability to display status messages, serial and backplane statistics, and firmware revisions.

This module is a drop-in replacement for the Niobrara CNOS-001.

Gateway, Router & Protocol Converter

The CNOS-101 is simultaneously a router, and a protocol converter. Internally, the CNOS-101 has 3 ports: the two serial ports, and the PLC "port" (via backplane comms). The serial ports speak Modbus RTU or ASCII (master or slave), SY/MAX, PLOGIC, RNIM, mixed Modbus/SY/MAX, and others. Messages from any of the three ports can be routed out any other port. As messages move between the ports they are translated from one protocol to another. Using an MSTR instruction, the PLC can issue:

  • 0x, 1x, 3x, and 4x MSTR reads via a serial port.
  • 0x and 4x MSTR writes via a serial port.
  • SY/MAX, PNIM, RNIM reads and writes via serial port.
  • Configuration commands to the CNOS.

The two serial ports have RJ45 connectors and are independently swich-selectable RS-232 or RS-422/485. Ports are independently configurable as to mode, baud rate, and etc. External serial devices can:

  • Read or write PLC registers.
  • Program the PLC.
  • Read or write Modbus, SY/MAX, or PowerLogic devices the other serial port.
    • Even program serial Modbus or SY/MAX PLCs.
  • Configure the CNOS.


  • TSX Compact PLC (-258, -265, -275, -285 only).
  • Free slot in the main rack (slots 3, 4, or 5).
  • Compact PLC Executive version 2.07 or greater. The Compact Executive required for the CNOS-101 is now available at Schneider Automation's website.


Multiple CNOSs can work in a single rack. Modules come with a user manual and configuration software on CD, 1-year warranty and 1-year free firmware upgrades.


The CNOS-101 is available as: CNOS-101 with two selectable (RS-232 or RS-485) serial ports.

Effective 26 March 2008 - Specifications subject to change without notice.