Product Overview

The Honeywell MLL-C21A is a dedicated RS-232C communication interface module designed for the MasterLogic PLC series. This unit functions as a remote access bridge, enabling serial modem connectivity for industrial control systems. It is primarily utilized for remote diagnostics, program management (uploading and downloading), and supervisory control from off-site locations.

By providing a reliable link between the PLC backplane and external telecommunication hardware, the MLL-C21A allows engineers to maintain system oversight without physical presence on the factory floor. It is a critical component for distributed automation architectures that rely on point-to-point (1:1) or multi-drop (1:N) serial networks to synchronize data across broad geographical areas.

Key Technical Characteristics

• Advanced Protocol Versatility: Supports the MLDP protocol for native Honeywell MasterLogic integration, as well as industry-standard Modbus RTU and Modbus ASCII master configurations.

• Remote Management Capabilities: Facilitates full remote operational control, including the ability to perform firmware updates, logic modifications, and real-time monitoring via a modem link.

• Flexible Network Topologies: Capable of managing 1:1 connections or 1:N architectures, allowing a single master station to coordinate with multiple slave devices.

• Configurable Serial Parameters: Offers user-definable parity settings (Odd, Even, None) and station addressing ranging from 0 to 31, ensuring compatibility with diverse legacy and modern serial peripherals.

• Simultaneous Connection Support: Enables concurrent remote sessions using MLDP or Modbus Server, optimizing data throughput in complex, multi-user automation environments.

• Software-Driven Configuration: Integration with SoftMaster-NM allows for streamlined setup, port parameter definition, and network synchronization.

• Asynchronous Transmission: Employs reliable asynchronous communication modes to ensure stable data packets even across long-distance serial runs.

Technical Specifications

• Manufacturer: Honeywell

• Model Number: MLL-C21A

• Module Type: Communication Modem / RS-232C Interface

• Communication Port: 1 Channel RS-232C

• Protocols: MLDP, Modbus RTU, Modbus ASCII

• Addressing Range: Station 0 – 31

• Power Supply: Provided via PLC Backplane

• Weight: 0.4kg

• Dimensions: 7 x 14 x 14.5cm

• HS Code: 8537101190

• Product Origin: USA

Industrial Application Areas

• Remote Infrastructure Monitoring: Managing pump stations, pipelines, and utility substations where onsite ethernet infrastructure is unavailable.

• Telemetry Systems: Transmitting process variables from remote sensors to a centralized DCS over telephone lines or radio modems.

• Machine Tool Integration: Connecting CNC or specialized manufacturing equipment to a master PLC for coordinated production cycles.

• Legacy System Bridging: Providing a modern serial gateway for older RS-232 based industrial hardware within a Honeywell MasterLogic environment.