The ControlLogix Controllers

Learn Logix Part 2.2. This article gives an overview of the features of the L7x and L8x ControlLogix series of controllers. It also explains the differences between the L7x and L8x ControlLogix controllers.

Learn Logix is a series of articles designed to teach you everything you need to know to work with Rockwell Automation’s Studio 5000 Logix Designer and the Logix 5000 series of PLCs.

In the last part of the series, we learned about the ControlLogix system and the components that make up the system. In this part of the series, we learn about the ControlLogix controllers that are part of the ControlLogix system.

The latest series of ControlLogix controllers are the L7x and L8x series. These series of controllers have many features in common, including;

Scrolling Display

Both the L7x and L8x ControlLogix controllers have a scrolling display that shows

  • Project name
  • Fault information
  • Firmware revision
  • Other data

This scrolling display allows someone to easily understand the status of a controller at a glance.

Secure Digital (SD) Memory Card

Both the L7x and L8x ControlLogix controllers use a Secure Digital (SD) card to provide non-volatile memory for the controller. This non-volatile memory is used to store the controller’s project.

USB Port

Both series of controllers have a USB port. This USB port is used to create a temporary point-to-point connection between the controller and a computer for transferring project files or monitoring program execution and system status.

Energy Storage Module (ESM)

Both controllers have an Energy Storage Module, also known as an ESM.

This ESM allows the controller to retrieve the project from non-volatile memory after power loss or a power cycle. The ESM also keeps the controller’s wall clock running for up to 5 days without power.

In the L7x controllers, the ESM can be removed from the controller using the Release button located on the front of the controller.

L8x Controller Features

The L8x builds on the features of the L7x controller. The enhancements of the L8x controller includes;

Better Performance

The L8x controller can deliver up to 20x faster scan times and up to 45% more storage than an equivalent L7x controller.

Gigabit Ethernet Port

L8x controllers feature a 1 Gigabit Ethernet port for fast communication over the ethernet network.

Increased Security

The L8x expands on the security features offered by the L7x controllers with;

  • Controller-based change detection and logging
  • Digitally signed controller firmware
  • Role-Based Access Control (also known as RBAC)

Role-based Access Control is a method of regulating access to a computer or network resources based on the roles of individual users within an enterprise. With RBAC, only specific users would be able to perform specific tasks like viewing, creating, or modifying files.


In this article, we learned more about the L7x and L8x ControlLogix series of controllers.

In the next part of the series, we will learn about the I/O modules available for the ControlLogix system. If you haven’t already, be sure to subscribe to the mailing list below to be notified when the next part is available.

Update: You can find the next part of the Learn Logix series, The ControlLogix I/O Modules, here. This article explains the features of the 1756 I/O modules, the I/O modules used in ControlLogix systems for local and distributed I/O.

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