PLX31-MBTCP-MBS4 | Prosoft Modbus TCP/IP to Modbus Master/Slave Gateway

Product Overview

The ProSoft PLX31-MBTCP-MBS4 is a Modbus TCP/IP to Modbus Serial (RTU/ASCII) 4-Port Gateway that enables high-speed bi-directional data transfers between Modbus TCP/IP-enabled PACs/SCADA systems and Modbus serial devices. Featuring four independent serial ports, this gateway can connect up to 400 Modbus serial devices (100 per port), dramatically reducing the number of gateways required in large-scale distributed automation systems. It is ideal for SCADA, power monitoring, and building management applications.

Key Specifications

• Part Number: PLX31-MBTCP-MBS4
• Product Type: Modbus TCP/IP to Modbus Serial 4-Port Gateway
• Series: ProSoft PLX30 Gateway Platform
• Ethernet Interface: 1 × 10/100 Mbps RJ45
• Serial Ports: 4 × RS-232/RS-485 (software selectable per port)
• Modbus TCP: Client (Master) and Server (Slave) modes
• Modbus Serial: RTU and ASCII (Master or Slave per port)
• Serial Device Capacity: Up to 400 devices (100 per port at 32 devices per segment)
• Configuration: ProSoft PLX50 Configuration Utility
• Power Input: 10–36 VDC
• Mounting: DIN rail
• Operating Temperature: -25°C to +70°C
• Storage Temperature: -40°C to +80°C
• Certifications: CE, UL, cULus, ATEX, IECEx (model dependent)

Features & Benefits

• Four Serial Ports: Independent RS-232/485 ports reduce gateway count and wiring complexity
• High Device Density: Supports up to 400 serial Modbus devices from a single Ethernet connection
• Dual Protocol Bridge: Transparently converts Modbus TCP to Modbus RTU/ASCII without PLC programming
• Flexible Port Configuration: Each port independently configurable as Master or Slave, RTU or ASCII
• Web Diagnostics: Built-in HTTP server for port status monitoring, traffic statistics, and firmware updates
• Conformal Coating Option: Available for corrosive or high-humidity environments

Applications

• SCADA systems polling large numbers of Modbus RTU flow meters and power monitors
• Building automation integrating legacy Modbus serial HVAC controllers into BACnet/IP over Modbus TCP
• Water/wastewater treatment with distributed Modbus serial pump controllers and valve actuators
• Solar farm inverter monitoring via Modbus RTU serial strings aggregated to central Modbus TCP SCADA

Installation Guide

1. DIN Rail Mount: Snap the PLX31-MBTCP-MBS4 onto a 35 mm DIN rail in an IP20 cabinet
2. Power Connection: Apply 24VDC (10–36VDC range) to the power connector
3. Ethernet Connection: Connect the RJ45 port to your Modbus TCP/IP network
4. Serial Wiring: Connect Modbus serial devices to Ports 1–4 using shielded twisted-pair cable
5. Termination: Install 120 Ω termination resistors at both ends of each RS-485 segment
6. PLX50 Configuration: Define Modbus TCP client/server settings and serial port parameters (baud, parity, mode)
7. Device Mapping: Map Modbus TCP registers to specific serial ports and slave addresses
8. Testing: Use the web interface to verify communication statistics on all four serial ports

FAQ

Q: Can all four serial ports operate simultaneously?
A: Yes, all four ports operate independently and simultaneously, each with its own baud rate and protocol settings.

Q: What is the maximum baud rate per serial port?
A: Each serial port supports baud rates up to 115.2 kbps (standard Modbus RTU limit).

Q: Does this gateway require a PLC?
A: No, the PLX31-MBTCP-MBS4 is a stand-alone gateway. It bridges Modbus TCP to serial without any PLC backplane requirement.

Q: Can I use RS-232 and RS-485 on different ports simultaneously?
A: Yes, each port is independently configurable as either RS-232 or RS-485 (2-wire or 4-wire).

Selection Tips

• Calculate total serial device count and divide by 100 to determine if one gateway is sufficient
• Use RS-485 (2-wire) for multi-drop networks; reserve RS-232 for single point-to-point connections
• Plan cable routing to keep each RS-485 segment under 1,200 meters for reliable 9600 bps operation
• For installations near VFDs or welding equipment, use shielded cable with proper grounding
• Order the conformal-coated variant for coastal, chemical, or wastewater treatment environments