Product Overview

The 1756-L55M12 is a high-performance central processing unit within the Allen-Bradley ControlLogix 5555 family. Engineered for large-scale industrial automation, this processor provides a robust platform for executing complex control logic and managing extensive I/O networks. It features 750 kbytes of user memory dedicated to data and program logic, alongside 208 kbytes of specific I/O memory.

This controller is designed for high-speed multitasking, allowing users to execute multiple programs simultaneously with varying priorities. While it utilizes volatile memory for rapid data processing, it relies on a battery-backed architecture to preserve program integrity during power loss. Its chassis-based design ensures seamless communication with other modules across the 1756 backplane, making it a cornerstone for distributed control systems.

Technical Characteristics

• Memory Capacity: 750 Kbytes User Memory; 208 Kbytes I/O Memory.

• Network Versatility: Supports integration with EtherNet/IP, ControlNet, DeviceNet, DH+, and Remote I/O via separate communication modules.

• Backplane Current Draw: 1.23 A at 5.1V DC; 0.014 A at 24V DC.

• Thermal Management: Power dissipation of 5.6W; thermal dissipation of 19.1 BTU/hr.

• Data Retention: Requires a 1756-BA1 Lithium Battery for volatile memory backup.

• Connectivity: Integrated RS-232 serial port compatible with 1756-CP3 and 1747-CP3 cables for programming and HMI interfacing.

• Redundancy Support: Capable of operating in redundant controller pairs when utilized within a ControlNet network architecture.

• Ruggedized Protection: Isolation voltage of 30V; tested to withstand 707V DC for 60 seconds.

• Environmental Limits: Operating temperature range of 0°C to +60°C; vibration resistance up to 2.0g at 10-500 Hz.

• Dimentions:14x14x14.5cm

• Weight: 0.36 kg (approx. 12.5 oz).

System Integration and Scalability

The 1756-L55M12 is optimized for demanding environments that require deterministic performance. Because it resides within the ControlLogix 1756 chassis, it can be combined with a vast array of digital, analog, and specialty I/O modules. Its ability to handle up to 32 tasks—one of which can be a dedicated periodic task—ensures that time-critical logic is executed with millisecond precision.

For mission-critical applications, this processor supports full controller redundancy. When paired with a second L55M12 and the appropriate redundancy modules, the system can perform an automatic switchover in the event of a primary processor fault, ensuring zero downtime for continuous processes. The processor's open-style enclosure and modular design facilitate easy maintenance and scalability as plant requirements evolve.