The forth generation of CompactLogix controllers began with the release of the L1, L2, and L3 back in 2012.

While 2012 might have been a bad year for Myan doomsayers, in was a banner year for the CompactLogix as Rockwell release not one but three new models.

While each model was physically different, unlike previous iterations all three shared a large number of features.

The 5370 Family of Small Programmable Automation Controllers:

One of the first things users noticed was that all three 5370 models had a USB 2.0 (Type B) programming port in place of the Channel 0 RS-232 port found on earlier CompactLogix controllers.

USB was not only more convenient than RS-232, it was also up to 15 times faster when flashing the controller's firmware.

Similar to the L4x line, all of the 5370 controllers used an internal capacitor in place of a battery, and they all had a button that could be used on power-up to erase the current program.

But unlike previous models, 5370 controllers had a Run Mode ‘toggle' switch in place of the classic ‘key' switch.

Also gone was the CompactFlash card slot found in the L3x and L4x, replaced with the more robust Secure Digital (SD) format. And unlike L3x and L4x models, all 5370 controllers actually came with a 1GB memory card.

5370 controllers also included a single Ethernet channel connected to a built-in, two port 10/100 Mbps Ethernet switch supporting star, linear, and ring typologies.

These new Ethernet channels had a substantially increased connection count (256 CIP, 120 TCP,) which was a boon to users who needed to connect multiple HMIs to a single CompactLogix.

Along with the additional CIP and TCP connections came a new, simpler means of determining the number of Ethernet I/O Nodes each model was capable of controlling.

Users no longer needed to ‘total up' the required connections of each I/O device as 5370 controllers had a ‘hard limit' to the number of I/O Nodes each could control.

These features, along with the fact that all 5370 were were roughly twice as fast as previous models, made them an instant hit with most of the existing user base.

And for the who were using the L4x series in motion control applications, that fact that select 5370 controllers (ERM models) also included support for motion over Ethernet made them a more cost effective option in most applications.

Good things come in threes. Well, at least when it comes to CompactLogix:

As previously stated, the 5370 family came in three unique lines: The L1, L2, and L3.

The L1 was the smallest of the three, reminiscent of the L23 but much smaller and with only Digital I/O built-in.

It was also the first controller to use 1734 Point I/O for local I/O Expansion.

Initially, three models were released:

Catalog NumberMemoryBuilt-In I/O (24vdc)Local 1734 I/O Modules:Ethernet I/O NodesCIP Motion Axis
1769-L16ER-BB1B384KB16 DI, 16 DO64
1769-L18ER-BB1B512KB16 DI, 16 DO88
1769-L18ERM512KB16 DI, 16 DO882

The L2 on the other hand was a direct replacement for the L23.

It came in both Digital Only, and Combination Digital and Analog versions like the L23, however its analog offered much higher resolutions as well as universal inputs.

The L2 was also 40% smaller than the L23, and all models supported up to four 1769 Compact I/O Expansion Modules.

Catalog NumberMemoryBuilt-In I/O (24vdc)Local 1769 I/O Modules:Ethernet I/O NodesCIP Motion Axis
1769-L24ER-BB1B750KB16 DI, 16 DO48
1769-L24ER-QBFC1B750KB16 DI, 16 DO, 4AI, 2AO, 6 HSC48
1769-L27ERM-QBFC1B1MB16 DI, 16 DO, 4AI, 2AO, 6 HSC4164

The L3 controllers launched as a direct replacement for the L3x line, supporting all of the 1769 I/O, Power Supplies, and Cables previously used with the popular L32E and L35E controllers.

The L30ER model brought a new, lower cost option to the line, while the ERM models added motion control (CIP Motion) support:

Catalog NumberMemoryLocal Expansion I/O ModulesEthernet I/O NodesCIP Motion Axis
1769-L30ER1MB8 in 1 bank16
1769-L30ER-NSE1MB8 in 1 bank16
1769-L30ERM1MB8 in 1 bank164
1769-L33ER2MB16 in 2 banks32
1769-L33ERM2MB16 in 2 banks328
1769-L36ERM3MB30 in 3 banks48


Even though it's been several years since the 5370 controllers were released, I still think of them as the pinnacle of the CompactLogix line.

Fast, easy to configure and use, and coming in multiple form factors, it has to be one of the most successful product launches in programmable controller history.

Well, that's how I feel… what do you think?

Have you used any of the 5370 controllers, and are you still using them? Or have you moved on to the newer 5380?

You can share your thoughts and opinions with us by clicking on the comment link below my signature.


Shawn Tierney
Automation Instructor and Blogger
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Forum Comments:
  1. Those fancy L1 series ended up being my micrologix replacement because it's worth the extra $$ over the micro800 line for future ethernet hookups and plant data collection. (There's quite a ban by lots of our customers on that micro800 platform entirely...) Also the PointIO is a good bus to keep in stock with the wide variety of small footprint cards available. In our project history we used the safety variant of the L3 - nice and powerful for monitoring those pesky E-Stops and gates and making up some safety zones.
    Thanks for the great series it was a good read all the way thru!
    Good morning ,
    Thanks for sharing your experience! I'm a fan of the L1 as well, and it's great that it can also control remote Ethernet I/O (unlike the Micros.)
    I also avoided the Micro800 until I had to teach a course on it, since then I do like it 🙂
    Oh, and there is one more article left - I picked up a 5380 to use in my Compact Basics course so I'll be writing about Gen 5 in the coming weeks 🙂
    Thanks for reading!!!
    This series is still by far my favorite CompactLogix group. I have used them on my smaller projects (primarily the L3) for the past several year. For my current project I ventured out and used a 5069-L306ER, it's nice but I'm wishing I would have stuck with the 5370 series, especially for the availability of getting modules from Rockwell.
    I think for the next go round I'll probably stick with my L3...
    Thanks for your comments. Yeah, I was a little stunned that they changed the I/O bit addressing (why change something that works?) and that there are no Encompass modules yet for the 5069 🙁
    Shawn Tierney,
    Instructor at The Automation School
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