ProSoft MVI69-MCM CompactLogix Modbus Communication Module

The ProSoft MVI69-MCM, also cataloged as the MVI69-MCM Modbus Master/Slave Network Interface Module, operates as a dedicated hardware component for multi-port serial data exchange within Rockwell Automation CompactLogix platforms.

Hardware Specifications

Protocol Conversion Latencies & Serial Networking

The module bridges the local 1769 backplane to standard Modbus networks, running up to two independent serial ports concurrently. Each interface is individually configurable to execute as either a Modbus Master or Modbus Slave using RTU or ASCII transmission formats.

Data transfers between the module memory registers and the CompactLogix processor are managed through small block transfers embedded in the asynchronous ladder logic scanning cycle. This internal arbitration system governs data mapping directly to user-defined arrays, ensuring that serial protocol conversion latencies do not introduce jitter into the time-deterministic operations of the main PLC backplane.

Frequently Asked Questions

Q: Can the MVI69-MCM module be removed or inserted into the 1769 chassis while backplane power is active?

A: No. Unlike larger 1756 architectures, the 1769 CompactLogix backplane system does not support Remove and Insert Under Power (RIUP) actions. Removing the module while the system is energized will trigger a fatal backplane bus fault on the controller and risk permanent electrical damage to the interface circuitry.

Q: How is the maximum current consumption bounded under full dual-port serial load?

A: The maximum internal power draw from the 1769 backplane is strictly limited to 800 mA at 5 VDC. External serial line loads, termination resistors, or transient voltage suppression states across both active lines are factored into this threshold, requiring correct sizing of the 1769 power supply budget.

Q: How are network node configurations maintained if the module encounters a total power loss scenario?

A: All protocol properties, mapping schemes, and port configuration matrices are permanently written to non-volatile onboard flash memory. Upon restoration of the 5 VDC backplane supply, the gateway initializes automatically from the stored profile without requiring a configuration download from the processor.

Field Installation Guidelines

• Chassis Attachment and Bus Interlocking: Power down the CompactLogix system prior to installation. Slide the module onto the standard 35 mm DIN-rail alongside adjacent 1769 components, ensuring the integrated tongue-and-groove guides align smoothly. Close the bus levers to firmly lock the backplane connectors together.
• Shielding and Grounding Infrastructure: Connect all serial communication networks using high-quality twisted-pair cabling. Ground the cable drain wire at a single point near the enclosure ground terminal block to suppress high-frequency electromagnetic field interference across the asynchronous serial paths.
• RS-485 Segment Termination: For networks operating at long physical distances or high baud rates up to 115.2 kbps, ensure a matching 120-ohm end-of-line resistor is attached across the balanced Tx/Rx lines at the terminal limits of the physical segment to prevent signal wave reflection.