Technical Specifications​

Backplane current 0.65 A at 5 VDC. Supported command list entries 100. Supported word reads and writes 125. Maximum Modbus registers 4000. Broadcast commands supported. Operating temperature 0 to 60 °C. Storage temperature -40 to 85 °C. Relative humidity 5 to 95 percent non-condensing. Weight approximately 2.31 lb or 1.05 kg.

Functional Features​

Dual serial ports configurable for master or slave operation. RS-232, RS-422 and RS-485 physical interfaces. Optical isolation for communication circuits. LED status indicators for diagnostics. Asynchronous data transfer between backplane and serial networks. Supports PLC 5, PLC 2 and PLC 3 integration through compatible 1771 chassis.

Application Scenarios​

Process control rooms, water and wastewater SCADA, motor drive networks, flow and temperature instrument polling, legacy PLC modernization, remote I/O communication through Remote I/O racks.

Performance Parameters​

Command list 100 entries. Data words 125 read or write. Register mapping up to 4000. Serial isolation level as specified by module revision; some references list 500 V optical isolation for backplane-related circuits and higher isolation for serial transceivers depending on configuration.

Material and Structure​

1771-style plug-in module with microprocessor, dual UART communication components, backplane interface circuitry and LED indicators. Two DB25 female serial connectors. Replaceable lithium-thionyl-chloride 1/2AA battery in configurations that require backup.

Working Principle​

The microcontroller manages backplane communication and serial protocol handling. One or both ports can be configured for Modbus RTU or ASCII. The module converts PLC data-table references into Modbus function calls, performs reads or writes to field devices, buffers responses and returns mapped data to the 1771 processor.

Installation Requirements​

Install in local 1771 rack or remote rack through Remote I/O. Verify rack power budget for 0.65 A at 5 VDC. Use proper DB25 cabling for RS-232, RS-422 or RS-485. Ground the chassis and serial shields according to Rockwell and ProSoft wiring rules. Configure node addresses, baud rate, parity and data format before placing the module online.

Usage Precautions​

Do not exceed 60 °C operating ambient. Avoid condensation and conductive dust. Confirm firmware and configuration software compatibility before replacement. Replace lithium battery using the specified 1/2AA type only. Verify ATEX or CSA permissions when used in hazardous locations.