Product Details

The ProSoft MVI71-MCM is a legacy single-slot Modbus serial communication module designed for Rockwell 1771 PLC-5 chassis platform, built to connect PLC-5 processors with Modbus RTU and ASCII compatible field devices. It is equipped with two independent isolated application serial ports, each port can be individually configured as Modbus master or slave, and supports jumper-selectable RS232, RS422 and RS485 electrical interfaces with optical isolation to reduce electrical interference from the field bus. The serial baud rate ranges from 110 baud to 115200 baud, users can configure parity, data bits, stop bits and RTS delay time to match the communication parameters of transmitters, meters and third-party controllers. It supports Modbus RTU with CRC-16 checksum and Modbus ASCII with LRC checksum, covering standard Modbus function codes for reading and writing coils, discrete inputs, holding registers and input registers. The module supports configurable floating-point data parsing, compatible with Enron and Daniel floating-point formats to solve byte order conversion problems for different Modbus devices. It has a built-in local register database for data buffering and mapping between Modbus network nodes and PLC-5 data files. A dedicated RS232 configuration port is used for downloading configuration files, online communication monitoring and fault diagnosis. The module exchanges data with the PLC-5 processor through BTR and BTW instructions over the 1771 backplane, so Modbus polling and message response will not occupy the PLC scan cycle and affect the real-time control logic. Sample ladder logic and configuration files are supplied for RSLogix 5, and ProSoft Configuration Builder software is used to set slave address list, polling commands and data mapping rules. This module is discontinued and only available as spare parts for legacy PLC-5 automation systems.

This module fits standard 1771 single-slot rack and consumes 800mA at 5VDC from the backplane. It supports hot-swappable operation for on-site replacement without shutting down the whole automation rack. Multiple LED indicators display module power status, backplane communication health, serial transmit and receive activity and configuration fault alarms for fast on-site inspection and troubleshooting. The operating temperature range is 0°C to 60°C, storage temperature ranges from -40°C to 85°C, with 5% to 95% non-condensing humidity tolerance. It meets industrial shock and vibration standards and adopts reliable EMC protection against surge and electrostatic interference. It supports configuration file backup and firmware upgrade for routine maintenance.

This Modbus serial master/slave module is widely used in water treatment, oil and gas, petrochemical, power distribution and factory automation renovation projects. It brings native Modbus serial connectivity inside the PLC-5 rack without external protocol converters, realizing stable data exchange with pressure transmitters, temperature sensors, flow meters, power meters and Modicon PLCs. As a discontinued legacy communication module, the MVI71-MCM is mainly supplied as spare replacement parts for running automation systems. It maintains stable Modbus serial data transmission, preserves the original field instruments and serial wiring, and reduces the renovation cost of Modbus serial network integration.