Product Overview

The Allen-Bradley 1756-L1M2 is a foundational CPU module from the ControlLogix® 5550 controller series, engineered to provide high-performance logic execution for industrial automation systems. Equipped with 1 MB of volatile user memory, this processor is designed for medium-scale applications requiring a multitasking operating environment without the need for onboard nonvolatile storage. It functions as the central intelligence within a 1756 chassis, coordinating complex operations across various I/O modules and network interfaces.

While categorized as a legacy component, the 1756-L1M2 remains a critical asset for maintaining existing infrastructure. It supports sophisticated control strategies including discrete, process, and motion control. Its open-style architecture allows it to be installed in any slot of a ControlLogix chassis, where it utilizes the high-speed Producer/Consumer technology to share data with other controllers and I/O devices efficiently.

System Connectivity and Communication

The 1756-L1M2 processor facilitates expansive system integration by bridging local and remote I/O via standard industrial networks. It is compatible with bridge modules for EtherNet/IP, ControlNet, and DeviceNet, as well as Universal Remote I/O. This networking versatility enables the controller to manage decentralized plant floor equipment while maintaining high-speed throughput.

For local configuration and programming, the module features an RS-232 serial port compatible with 1756-CP3 or 1747-CP3 cables. System data integrity is maintained during power cycles by the 1756-BA1 lithium battery, which provides the necessary energy to retain the user program in the volatile RAM. The module is also characterized by its robust electromagnetic compatibility, featuring high immunity to RF interference and electrostatic discharge (ESD).

Technical Specifications

• Manufacturer: Allen-Bradley (Rockwell Automation)

• Model Number: 1756-L1M2

• Series: ControlLogix 5550

• User Memory: 1 Megabyte (RAM)

• Nonvolatile Memory: None

• Backplane Current (5V DC): 1.05 A

• Backplane Current (24V DC): 0.02 A

• Power Dissipation: 4.8 Watts

• Thermal Dissipation: 16.4 BTU/hr

• Operating Temperature: 0°C to 60°C (32°F to 140°F)

• Relative Humidity: 5% to 95% (non-condensing)

• Vibration Resistance: 2 G @ 10–500 Hz

• Operating Shock: 30 G

• Replacement Battery: 1756-BA1

• Weight: 0.36 kg (0.8 lbs)

• Dimentions: 14.5x14x14.5cm

Hardware Resilience and Protection

• Industrial Hardening: Capable of withstanding up to 50 G of non-operating shock, ensuring durability during shipping and handling in heavy industrial environments.

• Electrical Isolation: Features a 30V continuous isolation rating, type-tested at 500V AC for 60 seconds to protect logic circuitry from field-side transients.

• Status Diagnostics: Front-panel LED indicators provide real-time feedback on controller health, battery status, and I/O activity.

• Emissions Compliance: Meets CISPR 11, Group 1, Class A standards for industrial radio-frequency emissions.