Migrating Allen-Bradley MicroLogix to Micro800 or CompactLogix
MicroLogix controllers sit on thousands of smaller UK machines: conveyors, case packers, wrappers, pumps and standalone process skids. Most of the family is now gone from Rockwell’s catalogue. Rockwell lists the MicroLogix 1000, 1100, 1200 and 1500 controllers as “discontinued and no longer available for sale”. Dates vary by catalogue number; for example the MicroLogix 1500 was discontinued on 30 June 2017, the 1200 controllers we checked in August 2021, and the 1100 controllers in April 2022.
The exception is the MicroLogix 1400: the 1400 controllers we checked are still shown as Active Mature (fully supported, but with a newer family to move to). Rockwell’s migration guide still covers it, and it is the obvious next family to plan for.
Micro800 or CompactLogix?
Rockwell’s migration guide maps each MicroLogix family to a Micro800 controller:
| From | Rockwell’s suggested Micro800 |
|---|---|
| MicroLogix 1000 | Micro820 or Micro850 |
| MicroLogix 1100 | Micro820 or Micro850 |
| MicroLogix 1200 | Micro850 or Micro870 |
| MicroLogix 1400 | Micro850 or Micro870 |
The MicroLogix 1500 is the odd one out: Rockwell points it to the MicroLogix 1400, or to a CompactLogix 5370 L1/L2 if you want to keep the existing 1769 I/O. Some 5370 controllers are now discontinued themselves, so check the specific catalogue number, or look at the CompactLogix 5380.
Do not specify a Micro830. It was discontinued at the end of 2023, even though some older Rockwell pages still name it as a target.
Rockwell does not give a single rule for choosing, so this is our view:
- Micro800 suits like-for-like replacement on a standalone machine. The Micro820 fits small machines with no expansion I/O. The Micro850 takes plug-ins and up to four 2085 expansion modules. The Micro870 is for larger standalone machines, with up to eight expansion modules.
- CompactLogix suits sites standardising on Studio 5000, machines that need integrated motion or more I/O than a Micro870 offers, and lines where the controller has to sit comfortably alongside ControlLogix and CompactLogix systems. It costs more per controller, but one platform and one software package across a site is worth something to the engineers maintaining it.
Converting the program to Micro800
Micro800 controllers are programmed in Connected Components Workbench (CCW), not RSLogix 500. Rockwell’s MicroLogix to Micro800 Converter runs from CCW; the current migration guide (February 2026) specifies converter version 5.07 with CCW version 23. You save the RSLogix 500 or RSLogix Micro project as a library file (.SLC) and import it.
Rockwell is direct about the limits: “Once the project is converted, you must make additional changes before it can be used.” The converter handles most instructions, ladder programs, basic I/O and documentation, and turns subroutines into user-defined functions. It does not convert:
- status file functions and data file properties
- indirect and indexed addressing
- controller configuration, I/O data tables and I/O configuration
- interrupts
- function files, which is where the high-speed counter and real-time clock lived
- passwords
Other changes to expect:
- Tags, not file addresses. Data files become arrays (N7:500 becomes N7[500]) and embedded I/O is renamed automatically (I:0/5 becomes _IO_EM_DI_05). Expansion I/O is not remapped, so every expansion point has to be reassigned by hand.
- Instructions fall into four groups: direct replacements, similar replacements (timers and counters), Rockwell function blocks that mimic MicroLogix behaviour, and placeholders you have to write yourself (PWM is an example). Anything unsupported appears as “UNK:”. Rockwell’s own guide shows a TOF being dropped in conversion, so check every timer.
- PID is not identical. Parameters and outputs are converted by hand.
- Data types. Many converted INT values feed Micro800 instructions that expect REAL, so type conversions are needed.
- High-speed counters are configured through CCW instructions rather than a function file.
CCW includes a Micro800 simulator, so the converted program can be tested before it touches the machine.
Converting to CompactLogix
Moving to CompactLogix means Studio 5000 Logix Designer and the PLC-5/SLC translation route. The conversion issues are the same family as an SLC 500 migration: arrays instead of data files, rescaled timers, rebuilt status and interrupt logic, and every flagged rung reviewed. Our SLC 500 to CompactLogix guide covers them in detail. Confirm early that your exported MicroLogix project will be accepted by the translation route you plan to use.
Hardware, comms and HMIs
- Expansion I/O does not carry over to Micro800. Micro800 uses 2080 plug-ins and 2085 expansion modules, and Rockwell’s migration tables replace 1762 expansion I/O with those parts. The Micro820 takes no expansion modules at all.
- Footprint and wiring change. A 24-point Micro850 is wider than the MicroLogix 1200 it replaces, terminal layouts differ, and some replacements need an external DC supply. Measure the panel before ordering.
- Communications. Micro820, 850 and 870 support EtherNet/IP, Modbus RTU and TCP, and DF1. Micro850 and 870 on recent firmware also accept PCCC commands, which helps existing SCADA, HMIs and MSG peers keep talking to them. DH-485 does not appear in Rockwell’s Micro800 protocol lists, so anything still on DH-485 needs a plan.
- HMIs. PanelView Component is discontinued and Rockwell recommends PanelView 800, also configured in CCW. Because Micro800 uses named tags, expect to repoint every HMI tag after conversion.
Before you start
- List every controller, expansion module, plug-in, HMI and comms link, with catalogue numbers, and check each one’s lifecycle status.
- Back up every program and check it matches what is running.
- Size the replacement with Rockwell’s Integrated Architecture Builder migration wizard, which proposes a Micro800 controller and plug-ins to match the I/O.
- Compare wiring and dimensions before committing to a like-for-like swap.
- Convert, then work through the not-converted list: interrupts, I/O configuration, HSC, PID, indirect addressing.
- Test in the simulator, then on hardware, before the machine is handed back.
Buying MicroLogix spares from unofficial channels is tempting while a migration is planned. Check provenance and firmware revision, and test before fitting.
How ECS approaches it
MicroLogix migrations are usually small individually and large in total: a site can have dozens of them across different machine builders. A Capture audit finds every one, backs up the programs and shows which are discontinued, so the work can be prioritised by risk rather than by whichever fails next. Converted programs, software versions and cables are held in Command Centre.
We carry out the conversions, panel retrofits and commissioning in-house as part of our automation projects, usually machine by machine around production.
Sources
- Rockwell Automation, MicroLogix Controllers to Micro800 Controllers Migration Guide (2080-RM002), February 2026
- Rockwell Automation, MicroLogix 1100, MicroLogix 1200 and MicroLogix 1500 family pages, and product pages for 1764-LSP and 1766-L32BXB, checked October 2026
- Rockwell Automation, Micro830 controllers and CompactLogix 5370 controllers
- Rockwell Automation, PanelView Component and PanelView 800
Lifecycle statuses and dates change. Check a specific catalogue number on Rockwell’s site before buying or planning around it.