CompactLogix 1769-L32E vs 1769-L36ERM

Overview

In the world of industrial automation, Rockwell Automation’s Allen-Bradley CompactLogix platform has served as a reliable workhorse for small to mid-sized applications for over two decades. However, the evolution of control technologies has created a massive generational gap between legacy units and modern, high-performance controllers.

This comparison analyzes two highly popular controllers from different eras within the 1769 platform family: the legacy CompactLogix 1769-L32E and the modern CompactLogix 5370 1769-L36ERM.

The 1769-L32E was introduced in the early 2000s to bring integrated EtherNet/IP connectivity to the CompactLogix form factor, bridging the gap between small standalone machines and larger ControlLogix systems. While it powered thousands of manufacturing lines globally, Rockwell Automation transitioned this unit to "End of Life" status.

Conversely, the 1769-L36ERM represents the high-end output of the CompactLogix 5370 L3 family. Sporting dramatically expanded memory, dual Ethernet ports with Device Level Ring (DLR) capabilities, integrated CIP Motion over EtherNet/IP, and a maintenance-free battery-less design, it is the premier direct-replacement path for older 1769 legacy installations.

For control engineers, maintenance managers, and system integrators planning system lifecycles, understanding the technical differences between these two modules is critical for scheduling downtime, maintaining spare parts inventory, and planning seamless modernizations.

Key Differences at a Glance

The transition from the L32E to the L36ERM is not merely an incremental speed increase; it represents an architecture shift from single-core processors with legacy serial ports to modern dual-core processors with embedded network switches.

The following evaluation table highlights the primary generational differences between these two control platforms:

Specifications Comparison

To select the appropriate controller or execute a successful system conversion, you must evaluate electrical, physical, and environmental parameters. The table below lists the technical specifications for both controllers:

Performance & Capabilities

The performance gap between the 1769-L32E and the 1769-L36ERM is distinct. Under the hood, the 1769-L32E relies on legacy processing architecture that executes standard program structures linearly. Complex floating-point math, high-frequency PID loops, and heavy string manipulation can quickly drag down its scan times.

Furthermore, the L32E's performance is heavily constrained by its tight memory limits. With only 750 KB of user memory, programmers in the mid-2000s had to limit visual descriptions, keep tag names short, and use minimal structured text.

The 1769-L36ERM utilizes a modern dual-core processing engine. One core is dedicated exclusively to executing the control program code, while the other core manages background system tasks, backplane data transfers, visual diagnostics, and EtherNet/IP communication traffic. This parallel design prevents communication spikes from interrupting deterministic logic execution.

The L36ERM boasts 3 MB of user memory—four times that of the L32E. This allows programmers to write descriptive tag names, make deep use of complex User-Defined Data Types (UDTs), implement standard Add-On Instructions (AOIs), and store comprehensive rung comments directly on the controller without running out of space.

Additionally, the L36ERM introduces native CIP Motion on EtherNet/IP, handling up to 16 synchronized axes of motion. This renders the old legacy systems of external analog servo modules or expensive SERCOS fiber-optic cards completely obsolete.

With the L36ERM, drives like the Kinetix 5500 can connect directly to the standard controller network, drastically reducing cabinet footprint and wiring complexity.

Programming & Software

The programming software ecosystem represents another generational leap. The 1769-L32E belongs to the era of RSLogix 5000. Because of its older processor architecture, its firmware support officially caps out at version 20.05. It cannot be programmed with any software version beyond v20, restricting your engineering environment to legacy interfaces that lack modern development utilities.

On the other hand, the 1769-L36ERM runs on Studio 5000 Logix Designer, supporting firmware versions from v21 up to the very latest active releases (v35+). This opens access to advanced development features, including:

• Modular Logical Organizer: Better structural sorting of systems beyond the traditional task-program-routine format.
• Built-in Component Diagnostics: Deep, integrated device profiles with dynamic drive and device control features.
• Enhanced Security Policies: Role-based access control, digital signatures, and firmware encryption to align with modern industrial cybersecurity frameworks (such as IEC 62443).
• Modernized Language Editors: An enhanced Structured Text editor with code folding, inline monitoring, and auto-completion helper utilities.

While RSLogix 5000 and Studio 5000 share a fundamental Logix instruction framework, trying to manage an L32E on a modern machine floor requires maintaining older virtual machines configured with legacy operating systems to run older software versions. Upgrading to the L36ERM streamlines development onto a single, modern programming platform.

Communication & Networking

The primary technical catalyst for upgrading from an L32E to an L36ERM is often network topology and port availability.

The 1769-L32E features one RJ45 Ethernet port and one RS-232 serial DB9 port:

• The Single Ethernet Port Problem: The L32E has a single Ethernet port that does not integration-hop. If you want to connect a programming PC, an HMI, and an upstream SCADA system, you are forced to install an external industrial Ethernet switch (e.g., Stratix) inside the control enclosure.
• The Serial Port Constraint: The L32E features an asynchronous serial port supporting DF1 or DH-485. This is highly useful for legacy bar code scanners or older panel displays, but it represents a security risk and an integration hurdle in modernized plants.

The 1769-L36ERM adapts to modern corporate-industrial network physical infrastructures by employing dual Ethernet ports that share a single IP address:

• Device Level Ring (DLR): The dual ports support ring topologies natively. If a single Ethernet cable in the machine ring is severed, data is rerouted in under a millisecond, preventing downtime and maintaining communication without expensive managed switches.
• Linear/Daisy-Chain Layouts: Devices can be daisy-chained from one controller to the next, optimizing cabinet space and reducing the run-lengths of your category-rated cabling.
• Socket Interfaces: Programmers can write custom raw socket interfaces to communicate with ASCII-based laser markers, scales, and RFID readers directly over Ethernet, entirely eliminating the old serial DB9 interface.

Pricing & Lifecycle

The lifecycle status of these two components heavily dictates their current financial value and risk profile:

• 1769-L32E (Lifecycle status: Discontinued/End of Life): Rockwell Automation no longer manufactures the 1769-L32E. OEM spare parts are restricted to residual inventories, and the secondary market consists of remanufactured, refurbished, or used units. While initial prices for bare components on the surplus market can sometimes seem low, the long-term risk of downtime due to component failure can be exceptionally costly when a replacement isn't readily available.
• 1769-L36ERM (Lifecycle status: Active Mature): This controller remains in active production and is fully supported by global Rockwell technical services. It is readily available from distributors like Palm Parts Solution. While it carries a premium list price reflection of its increased horsepower and capabilities, it establishes a reliable, decades-long system runway.

When to Choose Each

Selecting between these two parts depends on your operational goals, physical environment, and budget constraints:

Choose the CompactLogix 1769-L32E if:

• You need a direct legacy replacement: You are executing an emergency maintenance recovery on an existing line already engineered for an L32E, and you must avoid any code-base changes or software version changes during critical production hours.
• Legacy Serial Infrastructure is present: You have existing, unalterable DF1 serial connections that cannot use external Ethernet-to-serial conversion gateways.
• You are standardizing on RSLogix 5000 v20: Your plant operations are locked to a specific, certified codebase that cannot be migrated to Studio 5000 environment variants.

Choose the CompactLogix 1769-L36ERM if:

• You are upgrading or building new machines: You require a future-proof automation foundation with high-speed processing, DLR networking reliability, and a long support lifecycle.
• Integrated Multi-Axis Motion is required: Your application uses modern servo drives (e.g., Kinetix family) that require motion synchronization over a standard EtherNet/IP interface.
• You want to eliminate batteries: You want to eradicate routine maintenance downtime and avoid program loss due to dead 1769-BA lithium batteries.
• You are scaling local and remote I/O: Your physical I/O layout spans up to 30 local 1769 modules or requires extensive linkages to distributed remote point I/O drops (supporting up to 80 network nodes).

Migration & Upgrade Path

Migrating your controls from a legacy 1769-L23E/L32E/L35E to a modern 1769-L36ERM is a highly structured process. Because both units use the 1769 system bus, you can often preserve your physical local I/O modules, which considerably reduces hardware replacement costs.

Here is the technical migration path to execute a successful upgrade:

Step 1: Analyze Hardware Footprints and Power Requirements

Before making changes, verify that your rack configuration aligns with the power profile of the new controller.

1. Remove the L32E: Detach the L32E controller from the left-most slot of the 1769 backplane.
2. Evaluate Power Consumption: The L36ERM draws significantly more 24V DC backplane current (225 mA) than the L32E (10 mA). Review your existing 1769 system power supply configuration (e.g., 1769-PA2, 1769-PB2, or 1769-PA4). Ensure the power supply can support the newly balanced load, keeping in mind the distance rating of the active modules from the power supply.
3. No Additional Modules Needed: The L36ERM mounts directly to the existing 1769 DIN-rail scheme and plugs into the remaining 1769 I/O modules.

Step 2: Code Base and Software Conversion

To update your logical control program:

1. Open your existing .ACD project file in RSLogix 5000 (v20 or lower).
2. Save a backup of your original project before initiating conversions.
3. Go to Controller Properties and select Change Controller.
4. Select the 1769-L36ERM from the list of available controllers. This action automatically prompts you to migrate the software environment from RSLogix 5000 to Studio 5000 Logix Designer (v21 or greater).
5. Select your preferred target firmware. It is highly recommended to use the latest stable release (such as v32 or v33) to maximize cybersecurity and execution features.

Step 3: Address Compilation Errors & Serial Protocols

Changing the controller type changes the target physical hardware profiles, which can generate configuration warnings:

1. Check Serial Channels: The L36ERM does not have a serial channel. If your legacy code utilized system channels (Channel 0) for DF1 or DH-485 messaging instructions, those instructions will fail to compile. You must rewrite those communication schemes to use EtherNet/IP messaging or integrate an external Modbus/Serial gateway (e.g., ProSoft Technology modules).
2. Review Alias Tags: Verify that all your physical I/O mapping references updated successfully to point directly to the modified slot layout.
3. Compile and Download: Run a full project verify check. Once error-free, connect to the L36ERM via USB or Ethernet and download the newly compiled code.

Frequently Asked Questions (FAQ)

1. Can I reuse my existing 1769 expansion modules when upgrading to the 1769-L36ERM?

Yes. The 1769-L36ERM is fully compatible with existing 1769 local modular physical architectures (such as 1769-IQ16, 1769-OB16, 1769-IF4, etc.). However, you must recalculate backplane power supply loading. The L36ERM draws more 24V DC power than the older L32E.

2. Does the 1769-L36ERM require a battery replacement program?

No. Unlike the legacy 1769-L32E, which relies on the 1769-BA lithium battery to retain volatile RAM during power disruptions, the 1769-L36ERM uses a maintenance-free energy storage capacitor. On power loss, this capacitor provides sufficient energy to write all volatile memory tags directly to internal flash memory, eliminating routine battery replacement schedules.

3. How do I choose between the 1769-L36ERM and the newer 5069 CompactLogix controllers?

If you want to maintain your existing physical 1769 I/O card layout and minimize wiring changes, the 1769-L36ERM is the ideal direct-drop-in modernization solution. However, if you are designing a completely new system from scratch, the 5069 CompactLogix platform provides higher backplane speeds, gigabit Ethernet options, and uses the newer 5069 Compact 5000 I/O platform.

4. What happens to my HMI and SCADA devices when I replace the L32E with the L36ERM?

If you assign the exact same IP address to your new 1769-L36ERM, modern FactoryTalk View HMIs and SCADA systems (like Ignition or Wonderware) will communicate seamlessly without database modifications. The tag names and Logix structure remain identical. However, if your legacy display connected via the RS-232 serial DB9 port, you will need to upgrade the HMI to connect via Ethernet.

Related Articles

• Understanding RSLogix 5000 to Studio 5000 Upgrade Path
• How to Calculate 1769 Backplane Power Supply Budgets
• Industrial Protocols: Transitioning from Serial DF1 to EtherNet/IP