ProSoft MVI56-HART HART Master Multi-drop Network Interface Module

The ProSoft MVI56-HART, also cataloged as the MVI56-HART HART Master Multi-drop Network Interface Module, operates as a dedicated hardware component for multi-channel process instrument data acquisition within Allen-Bradley ControlLogix platforms.

Hardware Specifications

Process Control & HART Loop Connectivity

The interface module executes cyclic data transfer via the 1756 backplane using standard ladder logic and pre-defined data objects, appearing directly to the ControlLogix processor as a native Input/Output module. Each of the four channels features an independent 4-20 mA HART loop protocol engine, allowing concurrent multi-drop configurations.

The internal database stores digital primary variable data, secondary variables, and device status registers. By managing master protocol commands autonomously, the module handles up to 5000 internal registers without overloading the main PLC processor's scanning cycle. It maintains compatibility with HART field transmitters across more than 170 instrument models from over 105 manufacturers.

Frequently Asked Questions

Q: Does the MVI56-HART support online hardware replacement while the ControlLogix chassis is powered? A: Yes. The module is designed to slide directly into any standard 1756 chassis slot and supports hot-swapping under backplane power. However, pulling the module while active will instantly break the 4-20 mA digital instrumentation loop communication for all 60 connected field devices.

Q: Can a single channel mix different types of instruments, such as flow meters and pressure transmitters? A: Yes. Because each channel acts as a true HART master in multi-drop mode, you can connect up to 15 unique, parallel-addressed field instruments to a single channel, provided each device is assigned a distinct polling address between 1 and 15.

Q: How is the 4-20 mA analog signal loop power handled by this module? A: The module does not supply loop power directly to the field instruments. External 24 VDC process loop power supplies must be integrated into the field wiring architecture to power the connected field transmitters.

Field Installation Guidelines

• Chassis Grounding: Ensure the 1756 ControlLogix chassis is mounted securely to a grounded subpanel. The ground clips on the rear of the module must make firm, clean physical contact with the chassis rails.
• Shielding and Separation: Always route the 4-20 mA HART signal cables through dedicated low-voltage wire ways. Keep these cables separated from high-voltage AC motor lines or variable frequency drive (VFD) output cables to mitigate electromagnetic interference.
• Multi-drop Loop Impedance: To guarantee clean digital FSK (Frequency Shift Keying) signal modulation superimposed on the analog line, ensure that each loop contains a minimum loop resistance of 250 ohms between the external power supply and the module terminal block.