CAPP Products
      DIN Rail Products
      Modicon Products
      Square D Products
Download Area
Price List
Application Notes
NR&D Distributors
Compact Protocol Translator

Niobrara's CAT2 is a protocol converter that has been designed to allow Modicon® PLCs and other Modbus® slave devices to function reliably on RNIM networks. This compact unit, equipped with two RS-232 serial ports, translates serial communications between a device that uses RNIM protocol and a Modbus RTU slave device.

When using a CAT2 between a radio modem and a Modbus device, upstream master devices can read and write registers in the Modbus device and Modbus programming devices can be used to program a Modbus PLC.

On the front of the protocol converter there are two serial port connectors. Above each serial port are LEDs to indicate transmit and receive activity. Both ports use 9-pin D-subminiature connectors; port 1 is female, port 2 is male. This connector arrangement allows the cable that normally connects the radio modem and PLC to be used to connect the modem to the CAT2 and a standard Modbus programming cable to be used between the CAT2 and the PLC. The same cable can also be used to between a personal computer and the CAT2 during configuration.

On the bottom of the protocol converter there is a RUN/CONFIGURE switch. When set to the CONFIGURE position, serial port 1 is used to configure the unit. Configuration is accomplished using a personal computer running CAT2SW, the setup software supplied with each unit.

Each serial port can be individually configured as to baud rate and parity. Once configured, the RUN/CONFIGURE switch is set to RUN and the CAT2 communicates with the network devices through its serial ports, translating between the RNIM and Modbus devices. All configuration information is stored in the CAT2's EEPROM.

The CAT2 case is equipped with an integral DIN-rail mount. The unit is powered by 24 VDC; a 2-position screw terminal Weidmuller plug (included) connects to the power jack on the bottom of the CAT2 protocol converter.


Both port 1 and port 2 have the following pinout configuration:
Pin # Signal
1 no connection
2 RxD
3 TxD
4 Hi
5 Gnd
6 no connection
9 no connection


Dimensions: 0.9" wide by 3.0" tall by 5.5" deep (23 x 76 x 140mm). Case body is polycarbonate with an integral 35mm DIN-rail connector. Case front is rugged steel with baked on finish.

Power Requirements: 20 - 25 VDC, 175 mA (max.) through Weidmuller 13560.6 screw terminal plug (included).

Serial Ports: 9-pin D-subminiature connectors; port 1 female, port 2 male. 50, 75, 150, 300, 600, 1200, 1800, 2400,3600, 4800, 7200, 9600, 14400, and 19200 baud (Port 1); 300, 600, 1200, 1800, 2400, 3600, 4800, 7200, 9600, 14400, and 19200 baud (port 2); even or no parity. Supported protocols: Modbus RTU master, RNIM slave.

Indicators: Yellow transmit and receive indicators for both ports; four total indicators.

Setup Registers: The configuration of the unit is stored in processor equivalent registers; these registers are stored in EEPROM.


The CAT2 is available as:

CAT2 with two RS-232 serial ports.

Effective 01 February 1998 - Specifications subject to change without notice.