This guide covers the five Allen-Bradley controller families you will meet in US plants, the software that programs each one, and how tag-based and file-based addressing differ. It ends with a practical route into AB PLC programming, including where browser practice helps and where it stops.
Independent resource. Not affiliated with or endorsed by Rockwell Automation. Vendor facts checked against rockwellautomation.com on September 28, 2026.
An Allen-Bradley PLC is a programmable logic controller sold under the Allen-Bradley brand of Rockwell Automation, which is headquartered in Milwaukee, Wisconsin. Like any PLC, it runs a repeating scan. It reads its inputs (push buttons, photo eyes, proximity sensors, pressure switches, analog transmitters), solves the user program, then writes its outputs (contactor coils, solenoid valves, drive commands, indicator lights). What makes a controller “Allen-Bradley” in daily work is the ecosystem around it. That means the instruction names you read in the ladder, the addressing style, the programming software and the I/O and network hardware it connects to.
People searching for an “Allen-Bradley PLC controller” or “Allen-Bradley programmable logic controller” usually mean one of two things. Some are choosing hardware for a new machine. Others inherited a panel and need to know what is inside and which software opens it. Both questions start in the same place: identify the family. The family decides the software, the addressing style, the project file format and the lifecycle status. Those four things matter more than the brand name.
There is one split that trips up almost every new AB programmer. The modern Logix 5000 controllers (CompactLogix, ControlLogix and their GuardLogix safety versions) are tag-based and are programmed in Studio 5000 Logix Designer. The older MicroLogix and SLC 500 controllers are file-based and are programmed in RSLogix 500. The ladder symbols look almost the same. The way data is named and organized is completely different.
The families below cover nearly everything you will open as a controls technician or junior engineer in a US plant. Lifecycle notes reflect what Rockwell published on its product pages when we checked. Lifecycle status is set per catalog number, so always confirm the exact part in Rockwell’s Product Lifecycle Status tool before you buy spares or plan a migration.
| Family | Typical use | Programming software | Addressing | Lifecycle notes |
|---|---|---|---|---|
| Micro800 (Micro820, Micro850, Micro870) | Small standalone machines, simple skids and remote automation where a single compact controller is enough. | Connected Components Workbench | Named variables (IEC 61131-3 style) | Current family. Rockwell’s micro-controller page lists the Micro830 as discontinued. |
| MicroLogix (1000, 1100, 1200, 1400, 1500) | Small machines and packaged equipment; a large installed base across US plants and OEM equipment. | RSLogix 500 (the MicroLogix 1400 also works with RSLogix Micro) | File-based (I:0/0, B3:0/0, N7:0) | MicroLogix 1100 and 1200 are discontinued; the MicroLogix 1400 is still offered. |
| SLC 500 | Modular, chassis-based legacy control on older production lines. | RSLogix 500 | File-based | Rockwell says some SLC 500 bulletins are discontinued and recommends migrating to CompactLogix 5380. |
| CompactLogix (5380, 5390, 5480, Compact GuardLogix 5380) | Machine-level and mid-range control: packaging, material handling, OEM machines and smaller process skids. | Studio 5000 Logix Designer | Tag-based | Current family. Rockwell says some CompactLogix 5370 controllers are discontinued. |
| ControlLogix (5570, 5580, 5590, GuardLogix) | Large, multi-machine or plant-wide systems, process control and high-availability applications. | Studio 5000 Logix Designer | Tag-based | Current family. The ControlLogix 5590 was announced in October 2025. |
Rockwell’s current family for small standalone machines. The Micro820 targets small machine and remote automation jobs. The Micro850 and Micro870 add more I/O and communications for larger standalone machines. Micro800 controllers are programmed in Connected Components Workbench, not Studio 5000, and use named variables instead of MicroLogix-style data files. That matters if you are replacing a MicroLogix, because the program has to be converted as well as the hardware.
Compact, file-based controllers that shipped on a huge amount of packaged equipment. Rockwell lists the MicroLogix 1100 and 1200 as discontinued and points customers to Micro800. The MicroLogix 1400 is still offered. Our MicroLogix 1400 guide covers its data files, addressing, software, lifecycle status and migration paths in detail.
Modular, rack-based controllers that shared RSLogix 500 and file-based addressing with MicroLogix. Rockwell says some SLC 500 bulletins are discontinued and names CompactLogix 5380 as the migration target. RSLogix 500 includes a Logix Designer Export feature that converts SLC 500 ladder into a Studio 5000 project. Rockwell is explicit that the result still needs I/O mapping and review.
Both are Logix 5000 controllers, share Studio 5000 Logix Designer and support ladder diagram, structured text, function block diagram and sequential function chart. CompactLogix is the machine-level platform. ControlLogix is the chassis-based platform for large, multi-controller and high-availability systems. See our CompactLogix vs ControlLogix comparison for the numbers.
Studio 5000 Logix Designer programs CompactLogix, ControlLogix and GuardLogix controllers. Until version 20 it was called RSLogix 5000. Rockwell’s release notes describe version 21 as the first release that rebranded RSLogix 5000 as the Logix Designer application inside the Studio 5000 environment. That is why job postings still say “RSLogix 5000” for work that is done in Studio 5000 today. Projects are saved as .ACD files. Start with our Studio 5000 tutorial or the RSLogix 5000 tutorial, and see the Studio 5000 download guide for editions and system requirements.
RSLogix 500 programs the file-based MicroLogix and SLC 500 families, and saves projects as .RSS files. Rockwell has offered free entry-level editions for some small controllers, and which controllers each edition supports has changed over time. Our RSLogix 500 free guide explains what to check before relying on one. For a side-by-side of the two tools, read RSLogix 500 vs Studio 5000.
Connected Components Workbench programs Micro800 controllers. Studio 5000 Logix Emulate is Rockwell’s own software controller for testing Logix code without hardware, and it needs the Rockwell toolchain. If you only need practice rather than validation of a real project, our Logix Emulate alternative page and RSLogix simulator page explain the trade-off.
For HMI work, FactoryTalk View is the common pairing for Logix controllers. See the FactoryTalk download guide. Rockwell software licensing, editions and pricing change, so confirm the current terms with Rockwell or an authorized US distributor before you buy.
This is the biggest mental shift between RSLogix 500 and Studio 5000. The instruction may be the same XIC, but what it points at is named in a completely different way.
Data lives in numbered data files, each with a fixed type. On a MicroLogix 1400 the defaults are Output O0, Input I1, Status S2, Bit B3, Timer T4, Counter C5, Control R6, Integer N7 and Floating Point F8. Files 9 to 255 can be added for more storage of those types, and on the MicroLogix 1400 also for strings, long words, messages and PID. An address is built from file type, file number, element and sometimes a bit, so N7:12 is element 12 of integer file 7 and B3:0/5 is bit 5 of the first word in bit file 3.
The advantage is that an address tells you exactly where data sits. The drawback is that B3:2/7 means nothing without comments. Good RSLogix 500 programs lean heavily on symbols and descriptions.
In Studio 5000 you create tags with names and data types: BOOL, DINT, REAL, TIMER, COUNTER, arrays and user-defined types (UDTs). Tags can be controller-scoped, meaning visible to every program, or program-scoped, meaning local to one program. When you add an I/O module to the I/O configuration tree, the software creates module-defined tags for it. Most programmers then alias those to readable names such as Infeed_PE.
The advantage is readable, reusable logic. A UDT for a motor or valve can be copied across a whole line. The drawback for newcomers is that the physical wiring point is one step removed from the name in the rung, so tracing I/O means checking the alias.
| What you are addressing | File-based (RSLogix 500) | Tag-based (Studio 5000) |
|---|---|---|
| Physical input bit | I:0/3: input file, slot 0, bit 3 | A module-defined I/O tag, for example Local:1:I.Data.3 on a local 1756 digital input (the exact structure depends on the module) |
| Physical output bit | O:0/4 | A module output tag, often aliased to a readable name such as Conveyor_Run |
| Internal bit | B3:0/0 in the bit file | A BOOL tag with a descriptive name |
| Integer | N7:0: 16-bit signed integer | A DINT or INT tag |
| Timer | T4:0, with T4:0.ACC, T4:0.PRE, T4:0/DN | A TIMER tag, for example Fill_Delay.ACC or Fill_Delay.DN |
| Structure and reuse | Fixed file types numbered 0–255. Meaning lives in address comments and symbols. | User-defined data types (UDTs), arrays, aliases, controller-scope and program-scope tags. |
File types and numbering follow the MicroLogix 1400 Instruction Set Reference Manual (1766-RM001). I/O tag structures in Studio 5000 vary by module family and catalog number.
The families and the software differ, but the concepts below carry across every Allen-Bradley controller.
AB PLC training works best in layers. Each step below builds on the one before it, and each one links to a page on this site that goes deeper.
Understand that the controller reads inputs, solves rungs top to bottom and then writes outputs. Know why a normally closed stop button is usually examined with XIC, and why rung order matters. How to read ladder logic and learn PLC programming cover the ground rules.
Bit instructions come first: XIC, XIO, OTE and OTL/OTU. Then timers (TON, TOF and the retentive RTO) and counters (CTU and CTD, with RES to reset). Learn one-shots (ONS, OSR) and data instructions such as MOV and the compare instructions. PLC timers and PLC counters explain the accumulator, preset and done-bit model that AB timers and counters use.
Practice reading an RSLogix 500 rung full of I:0/3, B3:1/4 and T4:2/DN, then the same logic written with Studio 5000 tags and a UDT. If you can translate between the two in your head, you can support both the legacy panel and the new line.
A Logix project is organized into tasks (continuous, periodic, event), then programs, then routines. It also has an I/O configuration tree, controller-scope and program-scope tags, and add-on instructions. Knowing where to look is half of troubleshooting someone else’s code. Our Studio 5000 tutorial walks through it.
Start with motor start/stop, forward/reverse interlocks, conveyor timing, part counting and alarm latching. The motor start/stop, conveyor sort and traffic light scenarios, plus ladder logic examples, give you repeatable practice with pass/fail checks.
Going online, forcing I/O, downloading, matching firmware revisions, configuring EtherNet/IP modules and commissioning safety circuits all need Rockwell software, real equipment and a qualified supervisor. EtherNet/IP training and PLC troubleshooting prepare you. Formal options are compared in our Allen-Bradley training page and Allen-Bradley certification guide.
You do not need a controller or a Studio 5000 license to build the logic habits in steps 1, 2 and 5. This site’s Allen-Bradley PLC simulator includes an Allen-Bradley-style learning dialect. You declare tags against MicroLogix-style I:0/0 and O:0/0 addresses, then write rungs with XIC, XIO, OTE, OTL and OTU plus TON, TOF, CTU and CTD blocks. The program runs against a simulated machine and is graded on the behavior it produces.
A three-wire start/stop circuit in the learning dialect looks like this:
TAG START_PB I:0/0 BOOL
TAG STOP_PB I:0/1 BOOL // stop button wired normally closed
TAG MOTOR O:0/0 BOOL
[XIC START_PB OR XIC MOTOR] XIC STOP_PB OTE MOTORPress start and the motor output seals in through its own contact. Open the normally closed stop circuit and the rung goes false. That is the same reasoning you will use at a real panel.
What it does not do. The simulator is an independent learning tool, not Rockwell software. It does not open or save .ACD or .RSS projects, run Logix or MicroLogix firmware, or go online with a controller. The AB dialect is a subset. It does not support RTO, ONS, OSR or RES, and it does not model file types such as B3, T4 or N7, UDTs, add-on instructions or the Studio 5000 task model. Use it to drill logic. Use Rockwell’s tools, and Logix Emulate or real hardware, to validate a real project. The dialect compatibility notes and limitations page list the boundaries.
A free account includes 27 practice records and the first 6 core lessons in each dialect, including Allen-Bradley. You can run one guided program first without an account.
Vendor facts on this page come from Rockwell Automation’s own pages and publications. All were accessed on September 28, 2026. Product pages and lifecycle statuses change, so recheck them before you make purchasing or migration decisions.
Write a seal-in rung, add a timer, and watch the simulated machine respond. No install, no controller, no credit card.
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