ProSoft MVI46-MCM SLC Modbus Communication Module

The ProSoft MVI46-MCM, also cataloged as the MVI46MCM Modbus Master/Slave Interface Module, operates as a dedicated hardware component for asynchronous serial data conversion within Allen-Bradley SLC 500 platforms.

Hardware Specifications

Protocol Conversion Latencies & Backplane Arbitration

The module functions as a local input/output card interface between the Modbus serial network topology and the Rockwell Automation 1746 backplane. Data allocation within the hardware architecture uses an integrated 5000-word register memory segment to hold data values transferred between the foreign devices and the SLC processor.

The physical transmission of bits across the serial network link runs asynchronously from the backplane transfer cycle. This dual-port decoupling controls protocol conversion latencies, protecting the main SLC ladder program scan time from network polling delays. The configuration supports both Modbus Master and Modbus Slave roles to manage foreign data concentrator functions.

Frequently Asked Questions

Q: Does the MVI46-MCM module support hot-swapping or Remove and Insert Under Power (RIUP) actions within the 1746 rack? A: No. The 1746 chassis and backplane architecture do not permit online component extraction. System power must be isolated before sliding the module into or out of the slot to prevent physical circuit breakdown or hardware failure.

Q: How is data synchronized between the module's 5000-word register space and the SLC processor? A: Data routing uses M0 and M1 files driven by the SLC logic application. Because the memory block exchange runs asynchronously to the serial protocol loop, user logic handles the data block pagination without stalling the network transmission lines.

Q: What is the maximum current load drawn from the 1746 chassis power supply? A: The module demands 800 mA directly from the 5 VDC (up to 5.1 VDC) internal backplane rail. This current draw must be factored into the overall power budget calculations of the local 1746 power supply unit.

Field Installation Guidelines

• Chassis Insertion Restrictions: De-energize the 1746 chassis fully. Align the printed circuit board card guides into the target slot tracks of the rack and apply even pressure until the top and bottom plastic retaining tabs snap lock into place.
• Serial Wiring Shielding: Route all serial communication lines through dedicated low-voltage wire conduits. Use high-quality shielded twisted-pair cables, and ensure the drain wire terminates at a single low-impedance grounding bar within the control panel to block industrial electromagnetic interference (EMI).
• Line Termination Requirements: For long physical cable runs or configurations experiencing high signal reflection, connect a 120-ohm matching end-of-line resistor across the differential RX/TX lines on the termination blocks of the final network nodes.