ProSoft Technology MVI71-MCM Modbus Communication Module

Configured for bi-directional serial data transfer in Allen-Bradley PLC-5 systems, the ProSoft Technology MVI71-MCM (MVI71-MCM Modbus Communication Module) provides direct physical/electrical execution of Modbus RTU and ASCII protocol conversion across single-slot 1771 I/O chassis platforms.

Hardware Specifications

Protocol Conversion Latencies & Serial Bus Isolation

The MVI71-MCM minimizes protocol conversion latencies through localized buffer management within the single-slot 1771 module footprint. Internal memory maps execute up to 100 Modbus command blocks per port directly to the PLC-5 processor registers via high-speed Block Transfer Read/Write (BTR/BTW) cycles. Physical communication interfaces utilize isolated line drivers for RS-232, RS-422, and RS-485 topology configurations, preventing ground loops and transient surge coupling across serial networks up to 115.2 kbps.

Frequently Asked Questions

Q: How is data synchronized between the MVI71-MCM and the PLC-5 processor backplane?

A: Data transfer relies on standard Block Transfer Read (BTR) and Block Transfer Write (BTW) ladder logic instructions executed within the PLC-5 processor. Internal command blocks map Modbus register space directly into assigned backplane data files.

Q: Can both serial ports on the MVI71-MCM operate under different Modbus configurations simultaneously?

A: Yes, Port 1 and Port 2 are fully independent. Each port can be configured individually for Modbus Master or Slave functionality, running differing baud rates, parity settings, and physical layer standards (RS-232, RS-422, or RS-485).

Q: What is the backplane current draw restriction for installing this module in a 1771 I/O rack?

A: The module draws up to 800 mA at 5 VDC from the 1771 chassis backplane. Ensure the rack power supply has adequate current margin before inserting the module into an active backplane power group.

Field Installation Guidelines

1. Power off the target 1771 I/O chassis before inserting or removing the MVI71-MCM module. Do not perform hot-swapping during active operation.
2. Verify jumper block configurations on the module circuit board for RS-232, RS-422, or RS-485 operating modes prior to physical rack insertion.
3. Ensure proper grounding of all shielded serial cable braids to a single-point protective earth (PE) ground to mitigate common-mode EMI noise.
4. Maintain proper terminal connector torque and enforce standard NPT/metric cable gland strain relief rules to avoid physical port stressing.
5. Align module circuit board edge connectors with the 1771 backplane slot guides and press firmly until locked in place.