Honeywell 2MLL-C42A 2-Channel RS-422 Serial Communication Module

Product Overview

The Honeywell 2MLL-C42A is a 2-channel RS-422 serial communication module for the MasterLogic-200 (ML200) PLC system. It enables high-speed, noise-immune serial data exchange between the ML200 CPU and third-party devices such as barcode scanners, weigh scales, variable frequency drives, and legacy RS-422 instrumentation. With isolated channels and support for multiple protocols including Modbus RTU/ASCII, it serves as the backbone for integrated automation architectures.

Key Specifications

• Product Type: Serial Communication Module (RS-422)
• Series: MasterLogic-200 / ML200
• Channels: 2 (RS-422)
• Isolation: Channel-to-channel and channel-to-internal logic isolation
• Supported Protocols: Modbus RTU, Modbus ASCII, dedicated protocol, user-defined protocol
• Baud Rate: 300 bps to 115,200 bps (software selectable)
• Data Format: 7/8 data bits, 1/2 stop bits, odd/even/none parity
• Transmission Distance: Up to 1,200 meters (at 9,600 bps)
• Connection: 9-pin D-sub connector (per channel)
• Current Consumption: 40 mA (from 5V internal bus)
• External Power: DC 24V (20.4–28.8V) for interface circuits
• Dimensions (W x H x D): 27.4 mm x 90 mm x 70 mm
• Weight: Approx. 90 g
• Operating Temperature: 0°C to +55°C

Features & Benefits

• Dual isolated RS-422 channels — run two independent serial networks from one module, reducing communication module count by 50%
• Long-distance transmission — RS-422 differential signaling supports cable runs up to 1,200 meters, ideal for warehouse and material handling applications
• Multi-protocol support — built-in Modbus RTU/ASCII master and slave functions eliminate the need for custom protocol programming
• Galvanic isolation — protects the CPU from ground potential differences between the PLC cabinet and remote field devices
• High-speed 115.2 kbps — enables real-time data exchange with high-speed barcode readers and servo controllers

Typical Applications

• Barcode scanner and RFID reader integration on packaging lines
• Weigh scale and load cell indicator communication in batching systems
• VFD parameter read/write for pump and fan control
• Legacy PLC and DCS gateway integration via Modbus RTU
• Remote terminal unit (RTU) communication in water/wastewater SCADA
• Robotic controller serial interface for coordinate data exchange

Installation Guide

1. Install in I/O slot — mount the 2MLL-C42A in any available I/O slot of the ML200 main or expansion base.
2. Connect 24V external power — wire DC 24V to the external power terminals for the RS-422 interface drivers.
3. Wire RS-422 network — connect TX+, TX-, RX+, and RX- to the field device using twisted-pair shielded cable (minimum 0.5 mm²). Ground the shield at one end only.
4. Configure protocol in SoftMaster — set baud rate, data format, and protocol type (Modbus RTU master/slave or dedicated protocol) in the CPU parameter settings.
5. Test communication — use the SoftMaster monitor function to verify data register exchange with the connected device.

FAQ

Q: What is the difference between 2MLL-C42A and 2MLL-C42B?
A: The 2MLL-C42A is the standard RS-422 2-channel module. The 2MLL-C42B is a variant with potentially different connector orientation or conformal coating. Verify your system BOM for the exact suffix required. Electrical specifications are identical.

Q: Can I use this for RS-485 networks?
A: RS-422 is not directly interchangeable with RS-485 for multi-drop master-slave networks. For RS-485 applications, use the 2MLL-C42B or an external RS-422 to RS-485 converter.

Q: What is the maximum number of devices per channel?
A: RS-422 supports one driver and up to 10 receivers per channel. For multi-drop Modbus networks with >10 devices, use RS-485 topology instead.

Q: Does this module support protocol conversion?
A: The 2MLL-C42A supports Modbus RTU/ASCII natively. For protocol conversion (e.g., Modbus to Profibus), use the 2MLL-PMEA (Profibus Master) or 2MLL-PSEA (Profibus Slave) modules.

Selection Tips

• Select 2MLL-C42A for point-to-point or limited multi-drop RS-422 serial communication with drives, scales, and barcode readers.
• If you need RS-232C instead of RS-422, choose 2MLL-C22A (2-channel RS-232C).
• For mixed RS-232C and RS-422 on one module, select 2MLL-CH2A (1ch RS-232C + 1ch RS-422).
• Always use twisted-pair shielded cable for RS-422 runs >100 meters to prevent electromagnetic interference.