Allen-Bradley ControlLogix 1756-L55M16 Controller Module

Product Overview

The Allen-Bradley 1756-L55M16 is a high-capacity, high-performance programmable automation controller belonging to the premier ControlLogix® 5555 family. Engineered for complex, high-density industrial applications, this controller features an extensive 7.5 MB of onboard user memory dedicated to data and logic execution, complemented by 208 KB of high-speed I/O memory.

Architecturally, the module employs a unique dual-CPU design to parallelize operations. An internal Logix CPU executes the specialized control application code and communication messaging, while a dedicated backplane CPU independently manages real-time, high-speed data exchanges across the 1756 chassis backplane and local I/O modules. This dual-engine setup prevents process-logic execution drift during intense network broadcasting, maximizing total determinism.

Advanced Capabilities and Functional Benefits

• Dual-Processor Architecture: Splits the application workload. The dedicated logic engine runs the control loops, while the backplane processor manages deterministic I/O updates and messaging.
• Preemptive Multitasking: Supports up to 32 independent operational tasks (including periodic, event-driven, and continuous tasks) to allocate processor bandwidth efficiently based on real-time application priority.
• Producer/Consumer Network Tagging: Streamlines peer-to-peer data transfers. It broadcasts and receives system-shared tags across EtherNet/IP™ and ControlNet™ bridges without requiring intensive message instruction logic.
• Flexible Mixed-Language Support: Executes multiple native IEC 61131-3 programming languages simultaneously (Ladder Diagram, Structured Text, Function Block Diagram, and Sequential Function Chart) both online and offline.
• Comprehensive Fault Diagnostic Array: Features dedicated front-panel LED indicators—such as a flashing green I/O status indicator to quickly identify structural network or bridge card communication failures.

Technical Specifications

Memory & Execution Performance

• Module Classification: ControlLogix 5555 Processor Card
• User Data & Logic Memory: 7.5 MB
• Dedicated I/O Memory Matrix: 208 KB
• Maximum Discretes Supported: Up to 128,000 Total I/O Points
• Maximum Analog Capacity: 4,000 Input / 2,000 Output channels
• Baseline Program Scan Time: 0.08 milliseconds
• Non-Volatile Memory Backup: Requires a 1756-BA1 or 1756-BATM battery assembly

Electrical & Mechanical Properties

• Chassis Backplane Draw (5 VDC): 1.23 Amps
• Chassis Backplane Draw (24 VDC): 14 milliamps (0.014 A)
• Localized Programming Port: RS-232 Serial Port (Utilizes 1756-CP3 connection cables)
• Supported Networks: EtherNet/IP, ControlNet, DeviceNet, DH+, Remote I/O, SynchLink
• Operating Ambient Temperature: 32°F to 140°F (0°C to 60°C)
• Operational Vibration Tolerances: 10 to 500 Hz
• Relative Humidity Limits: 5% to 95% (Non-condensing)
• Hardware Dimensions: 3.5 cm (W) x 14.0 cm (H) x 14.5 cm (D)
• Net Hardware Weight: 0.37 kg (approx. 0.81 lbs)
• Country of Origin: United States (USA)
• Product Lifecycle Classification: Legacy Core (Active / Fully Supported for Spare Part Management)

Industrial Applications

• High-Density Automotive Assembly Lines: Managing high-speed synchronization between multiple DeviceNet robotic links and central assembly-line sequencing logic.
• Water and Wastewater Distribution Systems: Hosting extensive remote I/O configurations over EtherNet/IP networks across massive geographical treatment plant basins.
• Continuous Chemical Plant Blending: Utilizing concurrent Function Block and Ladder Diagram routines to tightly govern analog PID valves, level loops, and safety shutoff interlocks.
• Complex Material Handling Sorting Matrices: Executing rapid 0.08 ms instruction scans to manage sorting lanes and distribution systems processing thousands of high-speed sorting tracking data registers.