Modbus Master/Slave for ControlLogix and Logix-XT

Modbus Master/Slave Enhanced Network Interface Module for ControlLogix


The MVI56E Communication Module allows for Modbus Master and/or Slave connectivity from Rockwell Automation® ControlLogix® processors to Modbus RTU/ASCII devices. Each MVI56E port can be configured as a Master or Slave.

The MVI56E-MCM and MVI56E-MCMXT act as input/output modules on the ControlLogix backplane, making Modbus data appear as I/O data to the processor. Two independently configurable serial ports can operate on the same or different Modbus networks. The MVI56E-MCM is designed for standard process applications and the MVI56E-MCMXT is designed for the Logix-XT™ control platform, allowing it to operate in extreme environments. It can tolerate higher operating temperatures, and has conformal coating to protect it from harsh or caustic conditions.

A conformal coating option is available for this product.


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Features and Benefits

Backward Compatibility

  • All MVI56E products are backward-compatible with earlier MVI56 modules allowing direct replacement without the need to change existing controller programs

10,000 Word Database

  • Allows you to gather more data from your devices, which improves operational performance
  • Enjoy Enhanced features and flexibility without incurring expensive reprogramming costs

Add-On Instruction

  • Module configuration stored within the RSLogix™ 5000 project (ACD file)
  • No additional programming or configuration software is required
  • Add-On Instruction for RSLogix 5000 version 16 or higher cuts development time and costs

CIPconnect® Enabled

  • Facilitates remote user access across the ControlLogix backplane through Rockwell Automation’s 1756-ENBT module
  • Configure, diagnose, and analyze process data and communications status
  • Bridge through multiple ENBT/CNBT links to connect to MVI56E-MCMs installed in remote chassis for configuration and diagnostics

Add-On Profile

  • Simplifies adding the module in an RSLogix 5000 project


  • Backward-compatible with previous MVI56-MCM version
  • Single Slot - 1756 ControlLogix® backplane compatible
  • 10/100 MB Ethernet port for network configuration and diagnostics with Auto Cable Crossover Detection
  • User-definable module data memory mapping of up to 10,000 16-bit registers
  • 4-character, scrolling, alphanumeric 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
  • Supports RIUP (Remove and Insert Under Power)

Functional Specifications

The MVI56E-MCM will operate on a Local or Remote rack (For remote rack applications with smaller data packet size please refer to the MVI56E-MCMR product)

  • Supports Enron version of Modbus protocol for floating-point data transactions
  • PCB includes powerful Modbus network analyzer
  • Special functions (command control, event commands, status, and so on) aresupported by message transfer (unscheduled) using the MSG instruction
  • Error codes, network error counters, and port status data available in user data  memory

Slave Specifications

The MVI56E-MCM module accepts Modbus function code commands of 1, 2, 3, 4, 5, 6, 8, 15, 16, 17, 22, and 23 from an attached Modbus Master unit. A port configured as a Modbus Slave permits a remote Master to interact with all data contained in the module.This data can be derived from other Modbus Slave devices on the network, through a Master port, or from the ControlLogix processor.

Master Specifications

A port configured as a virtual Modbus Master device on the MVI56E-MCM moduleactively issues Modbus commands to other nodes on the Modbus network. Up to 325 commands are supported on each port. Additionally, the Master ports have an optimized polling characteristic that polls Slaves with communication problems less frequently.The ControlLogix processor ladder logic can issues commands directly from ladder logic or actively select commands from the command list to execute under ladder logic control.

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 implementations

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

Modbus Master Specifications

Command List

Up to 325 commands per Master port, each fully configurable for function code, slave address, register to/from addressing and word/bit count.

Optimized Polling

Configuration options allow Master ports and commands to be optimized to poll slaves with communication problems less frequently.

Command Status/Error Monitoring

Command Status or Error codes are generated for each command as it executes, allowing careful monitoring o fcommunication health between the Master and its Slaves.

Slave Polling Control

Master Port maintains a Slave Status list of all network Slaves. Polling of each Slave may be disabled and enabled using this list.

Modbus Slave Specifications

Full Memory Access

A port configured as a Modbus Slave permits a remote Master to read from or write to any of the 5000 registers that make up the user memory database.

Multi-source Slave data

Data presented at the Slave port can be derived from other Modbus Slave devices on a different network through the module's Master port or from the processor tag database.

Node address

1 to 247 (software selectable)

Status Data

Slave port error codes, counters and statuses are available separately for each port when configured as a Slave




Backplane Current Load

800 mA @ 5 Vdc, 3 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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