ControlLogix Enhanced Modbus Master/Slave Communications Interface Module with Reduced Data Block


The MVI56E-MCMR Enhanced Modbus Master/Slave Communication Module with Reduced Data Block allows Rockwell Automation® ControlLogix® processors to easily interface with devices using the Modbus RTU/ASCII serial communications protocol. Compatible devices include a wide variety of instruments, process measurement devices, popular brands of programmable logic controllers (PLCs) and programmable automation controllers (PACs).

The MVI56E-MCMR acts as an input/output module on the ControlLogix backplane, making Modbus data appear as I/O data to the processor. Backplane data transfers to and from the processor are asynchronous from communications on the Modbus network. Two independently-configurable serial ports can operate on the same or different Modbus networks. Each port can be configured as a Modbus Master or Slave, sharing the same user-controlled 5000-word database.

The MVI56E-MCMR utilizes a reduced Input/Output (I/O) data block for transferring data to and from a ControlLogix processor. This reduced data block makes it ideal for use in remote rack applications over ControlNet™. For EtherNet/IP™ applications where bandwidth is not an issue, it is strongly recommended to use the MVI56E- MCM.


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Features and Benefits



Backward Compatibility

  • All MVI56E products are backward-compatible allowing direct replacement of earlier MVI56 modules without the need to change existing controller programs
  • Enjoy Enhanced features and flexibility without incurring expensive reprogramming costs

Reduced Data Block

  • Reduced Data Block implementation requires less backplane/network bandwidth
  • Smaller data blocks are easier to schedule and transfer on ControlNet networks
  • Ideal solution for remote chassis installations using ControlNet and redundant controllers


  • ProSoft Configuration Builder software (PCB), with CIPconnect, facilitates remote user access across the ControlLogix backplane through Rockwell Automation's 1756-ENBT module
  • Configure, diagnose, and analyze process data and communications status
  • CIPconnect can bridge through multiple ENBT/CNBT links to connect to MVI56E-MCMRs installed in remote chassis for configuration and diagnostics

4-digit LED display

  • See critical configuration and status information without having to hook up to the ports


ProSoft Configuration Builder (PCB) provides a graphical configuration tool for quick and easy management of module configuration files, as well as viewing communication and module diagnostic information.

CIPconnect technology routes connections over multiple EtherNet/IP or ControlNet paths, allowing you to manage the module from remote locations.

The MVI56E-MCMR Setup Guide, with the sample configuration, provides step-by-step instructions on how to move data through the module from the  network to the processor.


  • Backward-compatible with previous MVI56-MCMR version
  • Single Slot - 1756 ControlLogix®  backplane compatible
  • 10/100 MB Ethernet port for configuration with Auto Cable Crossover Detection
  • User-definable module data memory mapping of up to 5000 16-bit registers
  • CIPconnect®-enabled network configuration and diagnostics monitoring using ControlLogix 1756-ENxT modules and EtherNet/IP® pass-thru communications
  • Sample Ladder Logic or Add-On Instruction (AOI) used for data transfers between module and processor
  • 4-character scrolling LED display of status and diagnostic data in plain English
  • ProSoft Discovery Service (PDS) software finds the module on the network and assigns a temporary IP address to facilitate module access and configuration
  • Personality Module (non-volatile CF card) to store all configuration settings, allowing quick in-the-field product replacement by transferring the CF card


Modbus General Specifications

Communication Parameters

Baud Rate: 110 baud to 115.2 kbps Stop Bits: 1 or 2

Data Size: 7 or 8 bits Parity: None, Even, Odd

RTS Timing delays: 0 to 65535 milliseconds

Modbus Modes

RTU mode (binary) with CRC-16 ASCII mode with LRC error checking

Floating Point Data

Floating point data movement supported, including configurable support for Enron and Daniel


Modbus Function Codes

1: Read Coils Status

2: Read Input Status

3: Read Holding Registers

4: Read Input Registers

5: Force (Write) Single Coil

6: Preset (Write) Single Register

8: Diagnostics

15: Force (Write) Multiple Coils

16: Preset (Write) Multiple Data Registers

17: Report Slave ID

22: Mask Write 4x Register

23: Read/Write 4x Registers




Backplane Current Load

800 mA @ 5 V DC3 mA @ 24 Vdc

Operating Temperature

0°C to 60°C (32°F to 140°F) - MVI56E-MCM
-25°C to 70°C (-13°F to 158°F) - MVI56E-MCMXT

Storage Temperature

-40°C to 85°C (-40°F to 185°F)


30g Operational
50g non-operational
Vibration: 5 g from 10 to 150 Hz

Relative Humidity

5 to 95% (without condensing)

LED Indicators

Battery Status (ERR)

Application Status (APP)

Module Status (OK)

4-Character, Scrolling, Alpha-Numeric LED Display

Shows Module, Version, IP, Port Master/SlaveSetting, Port Status, and Error Information

Debug/Configuration Ethernet port (E1 - Config)

Ethernet Port

10/100 Base-T, RJ45 Connector, for CAT5 cable

Link and Activity LED indicators

Auto-crossover cable detection

Serial Application ports (P1 & P2)

Full hardware handshaking control, providing radio, modem, and multi-drop support

Software configurable communication parameters

Baud rate: 110 baud to 115.2kbps

RS-232, 485 and 422

Parity: none, odd or even

Data bits: 5, 6, 7, 8

Stop bits: 1 or 2

RTS on/off delay: 0 to 65535 milliseconds

Serial Applications Ports (P1, P2)

RJ45 (DB-9M with supplied adapter cable)

Configurable RS-232 hardware handshaking

500V Optical isolation from backplane

RS-232, RS-422, RS-485 jumper-select, each port

RX (Receive) and TX (Transmit) LEDs, each port

Shipped with Unit

RJ45 to DB-9M cables for each serial port

5 foot Ethernet Straight-Thru Cable (Gray)


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