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The CNOE-900 is an Ethernet and serial option module for Schneider Automation's TSX Compact PLC. This modules give the Compact PLC a 100BaseT Ethernet port and two serial ports with all of the capabilities of the original CNOE-800 plus many others. The CNOE-900 includes an LCD screen and 5-button keypad which simplifies basic configuration such as setting the IP Address or serial port mode and baud rate. The LCD also provides the ability to display status messages, serial, Ethernet, and backplane statistics, and firmware revisions.

This module is a drop-in replacement for the Niobrara CNOE-800.

Gateway, Router & Protocol Converter

The CNOE-900 is simultaneously a router, and a protocol converter. Internally, the CNOE-900 has 4 ports: the Ethernet port, the two serial ports, and the PLC "port" (via backplane comms). The Ethernet port speaks Modbus/TCP and SY/MAX 802.3 protocols as both client and server. 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 four 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 over Modbus/TCP Ethernet.
  • 0x and 4x MSTR writes over Modbus/TCP Ethernet.
  • 0x, 1x, 3x, and 4x MSTR reads via a serial port.
  • 0x and 4x MSTR writes via a serial port.
  • SY/MAX 802.3 reads and writes via Ethernet.
  • SY/MAX, PNIM, RNIM reads and writes via serial port.
  • Configuration commands to the CNOE.

External Ethernet devices can use Modbus/TCP or SY/MAX 802.3 to:

  • Read or write PLC registers.
  • Program the PLC.
  • Read or write Modbus, SY/MAX, or PowerLogic devices on a serial port.
    • Even program serial Modbus or SY/MAX PLCs.
  • Bridge to the other Ethernet protocol, without PLC intervention.
  • Configure the CNOE.

An I/O scanning table allows the CNOE-900 to read and write Modbus/TCP devices over Ethernet. This table is confiugred via PC software (included) or MSTR instructions.

The two serial ports have RJ45 connectors and are independently selectable RS-232 or RS-422/485. These 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.
  • Program, read or write Modbus/TCP and SY/MAX 802.3 devices on the Ethernet.
  • Configure the CNOE.


  • 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 CNOE-900 is now available at Schneider Automation's website.


IP configuration can occur using the LCD and front panel keypad, over Ethernet via BOOTP or DHCP, or from the PLC via MSTR or conifg extensions*, or from the serial ports using Modubs or SY/MAX protocol. Multiple CNOEs can work in a single rack. No web pages are served by this module. Modules come with a user manual and configuration software on CD, 1-year warranty and 1-year free firmware upgrades.


The CNOE-900 Series is available as:
CNOE-900 with one 100BaseT Ethernet port and two selectable RS-232 or RS-422/485 serial ports

* Contact Schneider Automation for programming software that supports Ethernet configuration extensions for the Compact PLC.

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