Allen Bradley 1756-L1M2 ControlLogix 5550 Processor Module

Configured for high-speed logic execution in ControlLogix platforms, the Allen Bradley 1756-L1M2 (1756-L1M2 Processor Module) provides direct physical and electrical execution of user-defined control algorithms.

Suffix Breakdown & Model Matrix

The 1756-L1M2 is a standard ControlLogix 5550 series controller. The "L1" designation identifies the hardware generation, while the "M2" suffix denotes the integrated 1 MB expansion memory configuration. This module is compatible with standard 1756 series chassis and requires specific 1756-TBCH or 1756-TBS6H terminal blocks for field wiring termination.

Hardware Specifications

Profinet / EtherNet/IP Deterministic Networks

The 1756-L1M2 processor utilizes the ControlLogix backplane bus to maintain high-speed communication velocity between local I/O modules and the controller CPU. Deterministic execution is maintained through the management of task priorities within the backplane bus cycle. Users must ensure that firmware flash compatibility is verified against the specific ControlLogix chassis and communication modules to prevent timing violations. The I/O density scaling capabilities are governed by the backplane address capacity and the available memory allocation within the 1 MB storage limit.

Frequently Asked Questions

Q: Does the 1756-L1M2 support hot-swapping in a powered chassis?

A: Yes, this module supports removal and insertion under power (RIUP) in accordance with ControlLogix backplane specifications. However, the system must be in a state that allows for logical interruption of control processes.

Q: How does the module handle memory allocation for logic execution?

A: The 1 MB of onboard memory is utilized for project code, tag databases, and communication buffers. Exceeding the memory capacity will result in a controller fault, preventing the download of the project file.

Field Installation Guidelines

1. Chassis Preparation: Ensure the 1756 chassis is properly grounded to the enclosure frame to provide a low-impedance path for EMI/RFI shielding.
2. Insertion: Align the module with the guide rails in the designated slot. Apply even pressure until the top and bottom latches click into the locked position.
3. Power-Up: Verify that the 24 VDC or 120/240 VAC power supply is stable before energizing the chassis. The processor will perform a self-diagnostic sequence upon power-up.
4. Wiring Termination: When using 1756-TBCH or 1756-TBS6H blocks, ensure wires are stripped to the correct length and torqued to manufacturer specifications to maintain connection reliability.
5. Shielding: Ensure all communication and I/O wiring shields are terminated at the designated ground lugs provided on the terminal blocks or the chassis ground bar.