Honeywell 2MLL-CH2A Mixed Serial Communication Module RS-232C RS-422/RS-485

Product Overview

The Honeywell 2MLL-CH2A is a mixed serial communication module featuring 1-channel RS-232C and 1-channel RS-422/RS-485 for the MasterLogic-200 (ML200) PLC system. It provides flexible serial connectivity for applications requiring both local RS-232C programming/diagnostics and long-distance RS-422/RS-485 fieldbus communication on a single module. Supporting Modbus RTU/ASCII and user-defined protocols, it eliminates the need for two separate communication modules.

Key Specifications

• Product Type: Mixed Serial Communication Module (RS-232C + RS-422/RS-485)
• Series: MasterLogic-200 / ML200
• Channels: 2 (1x RS-232C, 1x RS-422/RS-485)
• RS-232C Connector: 9-pin D-sub (male)
• RS-422/RS-485 Connector: 9-pin D-sub (female)
• Isolation: 1500V on RS-422/RS-485 channel; non-isolated RS-232C
• Supported Protocols: Modbus RTU, Modbus ASCII, dedicated protocol, user-defined protocol
• Baud Rate: 300 bps to 115,200 bps (both channels)
• Data Format: 7/8 data bits, 1/2 stop bits, odd/even/none parity
• Transmission Distance: RS-232C: 15 m; RS-422/RS-485: 1,200 m
• Current Consumption: 40 mA (from 5V internal bus)
• External Power: DC 24V (20.4–28.8V)
• 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

• Mixed media on one module — RS-232C for local HMI/programming and RS-422/RS-485 for remote field devices, reducing module count by 50%
• 1500V isolation on RS-422/RS-485 — protects the CPU from ground loops and electrical noise on long fieldbus cable runs
• Modbus RTU/ASCII native support — built-in master and slave functions eliminate custom protocol programming
• Compact single-slot design — 27.4 mm width saves DIN rail space compared to installing separate RS-232C and RS-422 modules
• Independent channel configuration — each channel can operate at different baud rates and protocols simultaneously

Typical Applications

• Local operator panel (RS-232C) plus remote VFD network (RS-485) on one module
• Programming port (RS-232C) plus Modbus RTU fieldbus (RS-485) for maintenance flexibility
• Barcode reader (RS-232C) plus weigh scale network (RS-422) in packaging systems
• HMI connection (RS-232C) plus legacy PLC gateway (RS-485) in retrofit projects
• Any application requiring both short-range and long-range serial communication

Installation Guide

1. Install in I/O slot — mount the 2MLL-CH2A in any available ML200 I/O slot.
2. Connect 24V external power — wire DC 24V to the external power terminals for the interface drivers.
3. Connect RS-232C device — use a standard 9-pin D-sub cable to connect the RS-232C port to a programming laptop, HMI, or local device (max 15 m).
4. Connect RS-422/RS-485 network — wire TX+, TX-, RX+, RX- (RS-422) or A/B (RS-485) using twisted-pair shielded cable (max 1,200 m).
5. Configure channels in SoftMaster — set baud rate, data format, and protocol type independently for each channel.
6. Test both channels — verify RS-232C communication with a local HMI and RS-485 Modbus communication with remote devices.

FAQ

Q: What is the difference between 2MLL-CH2A and 2MLL-C42A?
A: The 2MLL-CH2A has 1x RS-232C + 1x RS-422/RS-485. The 2MLL-C42A has 2x RS-422 only. Choose CH2A when you need RS-232C for local programming or HMI; choose C42A for pure RS-422 fieldbus applications.

Q: Is the RS-232C channel isolated?
A: No. The RS-232C channel is non-isolated and intended for local connections within the same cabinet. The RS-422/RS-485 channel has 1500V isolation for fieldbus networks.

Q: Can I use the RS-232C channel for Modbus?
A: Yes. Both channels support Modbus RTU/ASCII. The RS-232C channel can communicate with a local Modbus device or HMI, while the RS-485 channel communicates with the fieldbus network.

Q: What is the maximum RS-485 device count?
A: RS-485 supports up to 32 devices per network (1 driver + 31 receivers). For larger networks, use repeaters or split across multiple modules.

Selection Tips

• Choose 2MLL-CH2A when you need both RS-232C (local) and RS-422/RS-485 (remote) on a single module.
• For 2x RS-232C, select 2MLL-C22A instead.
• For 2x RS-422/RS-485, select 2MLL-C42A or 2MLL-C42B.
• Always use shielded twisted-pair cable for RS-422/RS-485 runs >10 meters.
• Install termination resistors at both ends of RS-485 multi-drop networks to prevent signal reflections.