Description
ProSoft MVI56-LTQ | Limitorque Valve Network Interface Module for ControlLogix
Key Technical Specifications
| Parameter | Specification |
|---|---|
| Manufacturer | ProSoft Technology |
| Model | MVI56-LTQ |
| Module type | Limitorque Valve Actuator Master Communication Module |
| Host platform | Rockwell Automation ControlLogix |
| Host interface | ControlLogix backplane |
| Application ports | 2 serial ports, P1 and P2 |
| Serial interface | RS-232 / RS-422 / RS-485, configuration dependent |
| Baud rate | Software configurable; ProSoft documentation specifies 110–115,200 baud depending on protocol |
| Data bits | 5, 6, 7 or 8 |
| Stop bits | 1 or 2 |
| Parity | None, odd or even |
| Register space | 1,500 words |
| Valve capacity | Up to 150 valves |
| Backplane isolation | 500 V optical isolation |
| Configuration | Processor ladder logic / ProSoft configuration tools |
| Application | Limitorque valve actuator network |
| Status | Limited availability |
ProSoft describes the MVI56-LTQ as an I/O interface between the Limitorque valve network and the ControlLogix processor. Data exchange with the ControlLogix processor is asynchronous, while the module maintains a 1,500-word register space for transferring valve information and commands.
Product Introduction
The ProSoft MVI56-LTQ is an in-chassis communication module designed to connect a Rockwell Automation ControlLogix system with Limitorque valve actuators and other devices compatible with the Limitorque protocol. It occupies a ControlLogix chassis position and handles the serial network communication so the PLC application can work with valve status, position, faults, and operating commands through the module’s register interface.
The module provides two application serial ports and supports configurable serial communication parameters. ProSoft documentation specifies RS-232, RS-422 and RS-485 capabilities, with baud rate, parity, data bits, stop bits and RTS timing configurable according to the communication application.
MVI56-LTQ
Application Scenarios & Field Pitfalls — Engineer’s Perspective
Engineering Pain Point
The MVI56-LTQ is frequently mistaken for a generic Modbus serial module because it has serial ports. That classification is incorrect. Its primary purpose is Limitorque valve actuator network communication, so replacing it with an ordinary RS-485 communication card can leave the ControlLogix application without the required protocol and data-handling functions.
Typical Applications
- Motor-operated valve control — integrating Limitorque actuators into a ControlLogix-based plant control system.
- Process valve monitoring — transferring valve position, status and fault information into ControlLogix data registers.
- Water and wastewater systems — centralized monitoring and control of electrically actuated valves.
- Oil, gas and power systems — interfacing large groups of Limitorque MOVs with an existing ControlLogix architecture.
Technical Pitfalls to Avoid
- Do not substitute a generic serial module. The MVI56-LTQ contains application-specific Limitorque communication functionality; physical RS-232/RS-485 compatibility alone is not sufficient.
- Verify the valve network topology and active-slave configuration. The module supports a large valve address space, and the actual network configuration must agree with the ladder logic and actuator setup.
- Preserve the application configuration. ProSoft identifies module configuration, ladder files, system architecture, network details and serial-device information as important when troubleshooting an installation.
- Check serial interface selection carefully. The physical port uses an RJ45 connection with a supplied RJ45-to-DB-9M cable, so the RJ45 connector should not be interpreted as an Ethernet port.
Related Products
- ProSoft -MCM — general-purpose Modbus Master/Slave communication module for ControlLogix; different protocol application.
- ProSoft -BAS — BASIC communication/application module with serial interfaces; not a Limitorque-specific replacement.
- ProSoft -DNP — DNP 3.0 Master/Slave communication module for ControlLogix.
- ProSoft -101M — IEC 60870-5-101 Master communication module.
- ProSoft -104S — IEC 60870-5-104 Ethernet server communication module.
- Rockwell ControlLogix 1756-L7x — processor family commonly used as the host platform for in-chassis modules.
- Limitorque MX — electric valve actuator family that can form part of the valve network served by an LTQ application.
- Limitorque QX — another actuator family relevant to legacy Limitorque network installations.
Procurement Note
For a replacement , verify all of the following before purchase and installation:
- Complete part number:
- ControlLogix chassis and processor generation
- Existing ladder logic and module configuration
- Number of connected Limitorque actuators
- Serial network topology
- RS-232/RS-422/RS-485 interface arrangement
- Valve address/slave table
- Application firmware revision
- ProSoft configuration files and ladder/AOI documentation
Important: ProSoft’s current product page descrthe as limited availability, so a replacement project should preserve the existing configuration files and validate the proposed substitute at the system level rather than treating the module as a simple serial-interface spare.
