1756-L55M23 | Allen-Bradley | ControlLogix Logix5555 CPU Processor

Configured for high-speed logic execution in ControlLogix networks, the Allen-Bradley 1756-L55M23 (1756-L55M23 Logix5555 Processor) provides direct physical/electrical execution. This hardware unit manages up to 128,000 I/O points and utilizes a 1.5 MB RAM and 1.5 MB nonvolatile memory architecture to facilitate command processing and synchronized data exchange across the backplane bus.

Hardware Specifications

Profinet / EtherNet/IP Deterministic Networks

The 1756-L55M23 relies on deterministic backplane bus communication to synchronize state data across the ControlLogix rack environment. Effective I/O density scaling is constrained by the processor task scan times; users must ensure that total network overhead does not compromise the 0.08 ms program scan time performance. Firmware flash compatibility is mandatory between the controller and all distributed I/O bridges; users should verify current firmware revisions to maintain network determinism and prevent packet transmission errors.

Frequently Asked Questions

Q: Does the 1756-L55M23 support hot-swapping?

A: Yes. The module is designed for removal and insertion under power (RIUP) within a powered ControlLogix chassis, provided that system-level safety procedures for the specific application are followed.

Q: What is the purpose of the 1756-BA1 or 1756-BATM battery?

A: The battery maintains the volatile RAM content of the processor during power loss. If the battery voltage drops below specified thresholds, data integrity in the RAM can be compromised, requiring a reload of the project from the nonvolatile memory or an external programming terminal.

Field Installation Guidelines

• Slot Configuration: The processor must be inserted into an available slot within the ControlLogix chassis. Ensure the module is properly keyed and fully seated to ensure reliable backplane bus communication.
• Thermal Management: Install the chassis in an environment with sufficient convective airflow. The processor generates heat during operation; ensure the ambient temperature remains within the specified 0 deg C to 60 deg C range to prevent derating.
• Grounding and Shielding: Ensure the chassis is bonded to the equipment ground bus with a low-impedance connection. This mitigates electromagnetic interference (EMI) that can disrupt the high-speed backplane signals.
• Battery Handling: Install the 1756-BA1 or 1756-BATM battery into the battery housing on the front of the processor. Ensure the connector is fully inserted; replace the battery according to the status indicator signals on the front panel.