Allen-Bradley 1756-L55M24 Processor Module

Configured for high-speed logic execution and complex control tasks in ControlLogix chassis architectures, the Allen-Bradley 1756-L55M24 (1756-L55 Processor Module) provides direct physical/electrical execution. The controller integrates a 1756-L55 base unit fitted with a 1756-M24 memory card, establishing 3.5 MB of nonvolatile RAM for application program storage and tag database management. The processor interfaces directly across the local backplane to execute multi-tasking operating systems, managing cyclic I/O updating, data handling, and communication parsing without dedicated external coprocessors.

Suffix Breakdown & Model Matrix

Hardware Specifications

ControlLogix Deterministic Networks & Firmware Synchronization

The module communicates over the local ControlLogix backplane using EtherNet/IP deterministic networks and CIP interface logic. Backplane bus communication velocity allows deterministic, high-speed data exchanges between the controller and distributed I/O racks. Firmware flash compatibility via RSLogix 5000 / Studio 5000 enables non-destructive system updates, ensuring system synchronization across local backplane expansion slots without physical alterations to module memory boards.

Frequently Asked Questions

Q: Can the 1756-L55M24 controller module be inserted or removed under power (RIUP)?

A: Yes, the 1756-L55M24 supports Removal and Insertion Under Power (RIUP) within a ControlLogix chassis. However, removing an active processor halts all running controller tasks and forces connected output modules into their predefined fault states.

Q: How is memory retained on the 1756-L55M24 during a primary power loss?

A: Nonvolatile memory operation relies on the 1756-M24 memory board paired with an operational battery backup assembly (such as the 1756-BA1 or 1756-BATM) installed on the 1756-L55 base unit to preserve processor RAM state during system power cycling.

Field Installation Guidelines

• Verify chassis frame grounding satisfies IEEE 1100 standards by establishing a direct low-impedance connection between the chassis grounding stud and the enclosure star ground point.
• Align the module circuit board with top and bottom card guides of the assigned chassis slot, sliding the unit firmly until the top and bottom housing latches lock in place.
• Ensure the 1756-M24 memory expansion card is properly seated and mechanically secured to the 1756-L55 motherboard prior to inserting the complete assembly into the ControlLogix rack.
• Maintain a minimum clearance distance of 50 mm (2 inches) above and below the chassis assembly to preserve ambient air circulation across module cooling vents.