Allen-Bradley 1756-L55 ControlLogix Controller

The Allen-Bradley 1756-L55 ControlLogix Controller is a high-performance Logix5555 CPU designed for Rockwell Automation's ControlLogix systems, intended to govern large, deterministic I/O and process control within a 1756 backplane chassis. The 1756-L55M14 variant includes 1.5 MB of nonvolatile user memory for programs and data, supporting larger control projects while preserving data across power cycles. Catalog numbers in this family include 1756-L55, 1756-L55M12, 1756-L55M13, 1756-L55M14, and 1756-L55M16, giving options for different memory needs, firmware, and I/O configurations. This CPU is compatible with Rockwell's Studio 5000 / RSLogix 5000 software environments, with a maximum supported firmware/revision around v16 (and cannot be upgraded to newer v20+). In typical installations it acts as the central controller, executing ladder, function block, and structured text logic while coordinating communication with I/O modules and network devices via supported interfaces such as Ethernet-based controllers and backplane connections. For reliability in applications requiring nonvolatile memory retention, many configurations use the 1756-BA1 battery module to preserve critical data between power cycles. The L55 fits standard ControlLogix racks, relying on a 1756 backplane and compatible I/O modules to deliver scalable, modular control for manufacturing lines, packaging systems, and automated machinery that demand robust, long-term operation with a proven ecosystem.