MVI56-MCMR | Prosoft Modbus Communication Module

Product Overview

The ProSoft MVI56-MCMR is a dual-port Modbus RTU/ASCII Communication Module specifically optimized for remote rack installations in Rockwell Automation ControlLogix systems. It features two fully independent serial channels with DB9 connectors, supporting RS-232/RS-422/RS-485 software-selectable interfaces. Unlike the standard MVI56-MCM, the MCMR uses a compact data block approach that minimizes backplane bandwidth usage, making it ideal for installations across ControlNet or EtherNet/IP remote I/O networks.

Key Technical Specifications

• Product Type: Dual-Port Modbus RTU/ASCII Communication Module (Remote Optimized)
• Series: ProSoft MVI56
• Platform: Allen-Bradley ControlLogix
• Serial Ports: 2 × DB9 female connectors
• Interface Types: RS-232 / RS-422 / RS-485 (software configurable)
• Protocol Support: Modbus RTU, Modbus ASCII
• Channel Independence: 2 fully independent channels with different baud rates and protocols
• Baud Rate Range: 300 bps to 115.2 kbps
• Data Capacity: Up to 10,000 16-bit registers (internal storage)
• Backplane: 1756 ControlLogix (optimized for remote racks)
• Power Consumption: ~500 mA @ 5V DC (typical, dual channel full load)
• Configuration Port: 1 × RJ45 (10/100 Mbps) for Web server and diagnostics
• Serial Settings: None/Odd/Even parity, 5-8 data bits, 1-2 stop bits, RTS delay adjustable
• Configuration Tool: ProSoft Configuration Builder (PCB)
• Operating Temperature: 0°C to +60°C
• Storage Temperature: -40°C to +85°C
• Origin: USA

Key Features

• Remote Rack Optimized: Compact data block minimizes bandwidth over ControlNet/EtherNet/IP
• Dual Independent Channels: Each port runs different baud rates and protocols simultaneously
• High-Speed Communication: Up to 115.2 kbps for demanding applications
• Large Internal Database: 10,000-word storage for extensive device data
• Web-Based Diagnostics: RJ45 configuration port with built-in web server
• Flexible Configuration: PCB software with import/export capability
• Master/Slave Flexibility: Each port independently configurable

Critical Installation Note — Data Block Approach

Unlike standard MVI56-MCM, the MCMR uses a compact data block that does NOT automatically map to PLC I/O tags. You MUST use ProSoft's Add-On Instruction (AOI) or custom function blocks to read data from the module. Without periodic MCM_READ calls in ladder logic, the module LEDs will show green but data will remain at initial values.

RS-485 Wiring Best Practices

• For runs >100m or >10 nodes, install 120Ω termination resistors at both ends of the bus
• MVI56-MCMR does NOT have built-in termination jumpers — external resistors required
• Verify A/B polarity with multimeter (A should be ~2-6V higher than B when idle)

Applications

• Cross-facility energy data acquisition (multi-kilometer installations)
• Mixed-protocol packaging lines (Modbus RTU + ASCII simultaneously)
• Remote SCADA concentrator applications
• Bandwidth-constrained ControlNet/EtherNet/IP remote I/O

Installation Guide

1. Install in 1756 ControlLogix slot (local or remote rack)
2. Connect DB9 serial cables to Port 1 and Port 2
3. Set jumpers for RS-232/422/485 as required
4. Configure baud rate, parity, and protocol per port via PCB
5. Import AOI into Studio 5000 and add periodic MCM_READ calls
6. Map internal database to controller tags
7. Verify data flow via web diagnostics

FAQ

Q: What is the difference between MVI56-MCM and MVI56-MCMR?
A: MCMR is optimized for remote racks with compact data blocks; MCM is for local racks with automatic I/O mapping.

Q: Why is my MCMR showing green LEDs but no data?
A: You must use AOI or custom function blocks to read data. The module does not auto-map to I/O tags.

Q: Does it support floating-point data?
A: Yes, supports Enron and Daniel floating-point formats.

Model Selection Tips

• MVI56-MCMR = Remote-optimized Modbus module for ControlNet/EtherNet/IP remote I/O
• For local rack with auto I/O mapping, use MVI56-MCM
• For extended temperature, use MVI56E-MCMXT
• For Modbus TCP/IP, use MVI56E-MNETC
• Always verify AOI implementation in ladder logic for MCMR