The Allen-Bradley 1756-L81E, also cataloged as the 1756-L81E Programmable Controller Module, operates as a dedicated hardware component for high-speed logic execution and industrial network management within ControlLogix 5580 platforms.

Architecture & System Integration

The Allen-Bradley 1756-L81E occupies a single chassis slot within ControlLogix system backplanes (including 1756-A4, 1756-A7, 1756-A10, 1756-A13, and 1756-A17 standard/K series). The unit features 3 MB of user memory paired with a factory-included 2 GB 1784-SD2 Secure Digital card for non-volatile storage. Designed for energy efficiency, it utilizes an internal energy storage module to back up RAM data during power interruption, eliminating external lithium batteries.

Hardware Parameters

Deterministic Ethernet & Backplane Bus Communications

The integrated Ethernet port on the 1756-L81E supports deterministic EtherNet/IP networks operating at 10, 100, and 1000 Mbps for up to 100 nodes. High-speed backplane bus communication velocity enables rapid data transfer between the processor and local I/O cards. Asynchronous I/O execution processes updates independently of program scan routines. Firmware flash compatibility over network interfaces permits field upgrades without hardware modification.

Delivery Package Details

• 1 x 1756-L81E ControlLogix 5580 Controller Module
• 1 x 1784-SD2 2 GB Secure Digital Card (Pre-installed)
• 1 x Factory Sealed Protective Packaging

Installation & Wiring Framework

• Verify chassis backplane power is off before inserting or removing processor modules unless operating in non-hazardous locations.
• Align the module circuit board with the top and bottom chassis guides and push firmly until top and bottom latches secure.
• Connect Category 5e or Category 6 shielded industrial Ethernet cabling to the RJ45 port for 1 Gbps network operations.
• Ensure low-impedance grounding of the ControlLogix chassis to the main enclosure earth busbar to prevent noise interference.
• Avoid routing Ethernet communication cables in close proximity to high-voltage AC or variable frequency drive power cables.

Hardware FAQ

• What is the total current requirement from the backplane for the 1756-L81E?

  The controller draws 1200 mA at 5.1 VDC and 5 mA at 1.2 VDC from the backplane, resulting in total internal power dissipation of 6.2 W.

• Does the 1756-L81E require a lithium battery for RAM memory retention?

  No, the unit uses an integrated maintenance-free energy storage solution to write volatile memory to non-volatile memory during power loss.

• How many EtherNet/IP nodes are supported natively by the embedded port?

  The onboard RJ45 Ethernet port supports up to 100 EtherNet/IP nodes and handles speeds of 10, 100, and 1000 Mbps.

• What non-volatile storage card is compatible with this processor?

  The module includes and supports the 1784-SD2 2 GB Secure Digital (SD) card for non-volatile project backup and restore operations.

• Which ControlLogix chassis models accept the 1756-L81E processor?

  It mounts into any standard slot of ControlLogix 1756-A4, 1756-A7, 1756-A10, 1756-A13, and 1756-A17 chassis (including standard and conformal coated K-versions).

• How does asynchronous I/O execution affect logic programming on this model?

  Because I/O data updates asynchronously to the logic scan, critical input signals referenced multiple times within a single scan routine should be buffered.

• What maximum discrete and analog I/O point counts can this controller manage?

  The 1756-L81E handles up to 128,000 discrete input/output points and up to 4,000 analog input/output points across supported networks.

• What continuous isolation rating is specified for the 1756-L81E assembly?

  The module provides a continuous isolation voltage rating of 50 V between system logic circuits and the communication ports.