Today most major automation vendors have a Programmable Automation Controller (PAC) line, and Rockwell Automation is no exception with its CompactLogix and ControlLogix products.

In fact, Rockwell's “Logix” line of Programmable Automation Controllers are the most popular line of PACs used in North America today.

Automation-Fair-2014-Z-Panel2Early on, Rockwell's “Logix” controllers consisted of five different offerings:

Note: The Allen-BradleyMicroLogix” is not considered a PAC nor a member of Rockwell's “Logix” platform. It's actually based on their SLC-500 line of PLCs, and in my opinion it would have been less confusing if they had called it the Micro500 instead.

Automation-Fair-2014-Z-Panel3Since then, the ControlLogix and CompactLogix have become the dominate products in the line, with the FlexLogix going out of production back in 2009, and the SoftLogix and DriveLogix finding small niche markets a fraction of the size of the CompactLogix and ControlLogix.

While both the CompactLogix and ControlLogix program with the same software, the ControlLogix supports more demanding applications with higher I/O counts, while the CompactLogix is most often used in smaller systems or on OEM equipment.

The ControlLogix

The ControlLogix was the original Logix platform, and was first released back in 1999.

ControlLogix-HardwareIt's a modular system, and at a minimum consists of a Chassis, Power Supply, Processor, I/O modules and/or Communications modules.

Over the years the chassis and power supplies haven't changed all that much, but several generations of processors and network communication modules have been released.

The original processor released in 1999 was the 1756-L1, also know as the 5550 processor, and supported firmware versions 1 all the way up to
version 13

1756-L6xThe L1 was followed by the L55, or 5555, which is the only ControlLogix processor with expandable memory. In fact, you never want to order just a 1756-L55 as it will comes without any memory at all!

Following the L55 was the L6x, or 556x. It's notable for coming in two major versions, with the series B version having greatly improved battery life due to a redesign of the memory circuit.

The L6x was also the first ControlLogix processor to support CompactFlash for non-volatile memory, with features similar to the EEPROM functionality of older PLCs.

1756-L7xIn more recent times we've seen the release of the L7x, or 5570, which replaced the DB9 serial port found on all previous ControlLogix processors with a USB port.

The L7x also replaced the L6x's CF card slot with an SD slot, and even comes with a 1GB industrial SD card for use as non-volatile memory.

The L7 also improved on all previous ControlLogix processor designs by replacing the need for a battery with the inclusion of a removable super capacitor charging module.

And just last month Rockwell released its new L8x, or 5580 line of ControlLogix processors.

Although similar to the L7 line in many ways (USB port, SD Card Slot, Super Cap,) the L8 also comes with huge performance improvements (i.e. 5 to 20 times faster program scans) as well as an embedded 1GB Ethernet port.

For more details about Rockwell's new 5580 ControlLogix, see our previous article here.

All of the above ControlLogix products have catalog numbers beginning with 1756, and are detailed in Rockwell's ControlLogix Selection Guide.

The CompactLogix

CompactLogix-L1-L23The CompactLogix line comes in two styles: The all-in-one packaged controller, and the modular chassis-less system

Examples of the CompactLogix packaged controller include the last generation's L23 controller, as well as the current generation's L1xER and L2xER processors.

1769-L35EExamples of the modular system include the last generation's popular line of L32x and L35x processors, as well as the well received current generation L30ER, L33ER, and L36ER processors.

While the packaged controllers are ready to go out of the bock, all of the modular L3 models do require at a minimum a Power Supply as well as a Right End Cap, and most often will be paired with local Compact I/O.

It should also be noted that the current generation of L1, L2, and L3 CompactLogix processors are also know as the 5370 line, with the “70” indicating they share many of the improvements found in the ControlLogix L7 or 5570 processor, including:

  • CompactLogix-L36ERMEmbedded USB port in place of legacy DB9
  • SD card slot for use as nonvolatile memory
  • 1GB Industrial SD memory card included
  • New embedded super cap eliminates the need for a battery

All of the above mentioned CompactLogix products have catalog numbers which start with 1769, and are detailed in Rockwell's CompactLogix selection guide.

Learning more about CompactLogix and ControlLogix

If you'd like to learn more about Rockwell's CompactLogix and ControlLogix PACs, check out my new free PAC Getting Started course at

In it, I show you how to setup communications, flash firmware, download programs, and even how to use a timer and sequencer to automate your projects, as well as how to message data over Ethernet.


Shawn Tierney
Automation Instructor and Blogger

Have a question? Join my community of automation professionals and take part in the discussion! You'll also find my PLC, HMI, and SCADA courses at

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