L5X file: what it is and how to open, edit or convert one

An .L5X is what Studio 5000 Logix Designer writes when you export a project, or part of one, as XML. It turns up attached to emails, in version control, in migration projects, and on the desk of somebody without a Logix Designer licence who needs to know what is in it.

Rockwell documents the format in the Logix 5000 Controllers Import/Export Reference Manual, publication 1756-RM014. Everything below that is specific to the format comes from that manual or from the Logix Designer online help.

What an L5X is

Rockwell describes the .L5X file as an ASCII file structured with XML that you can open and modify in a text editor such as Notepad, or view in a browser and other tools that read XML.

It can hold two different things. A full project export carries the whole controller. A component export carries a selected piece and whatever it references. The online help lists the components that can travel as L5X: programs and equipment phases, routines and phase state routines in any language, ladder rungs, user-defined data types and string types, Add-On Instructions, trends, tag-based alarms and modules. It adds that the export includes referenced components an import will need, such as tags.

The useful accident of the format is that ladder logic inside it is not XML. Each rung is stored as Rockwell neutral text, the same notation people paste into forum posts: XIC(Start)XIO(Stop)OTE(Run);.

L5X, L5K, ACD and CSV compared

Rockwell's rule of thumb from 1756-RM014: for the entire project use L5K or L5X; for individual portions use L5X; for tags and logic comments use CSV or TXT. TXT is the one to pick for comments in Chinese, Japanese or Korean, because the CSV format does not support double-byte characters.

Inside the file

The root element is RSLogix5000Content, which carries version and export information. This is the example Rockwell prints in 1756-RM014, from a whole-controller export:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<RSLogix5000Content SchemaRevision="1.0" SoftwareRevision="26.00"
    TargetName="Controller_1" TargetType="Controller" ContainsContext="false"
    Owner="User, RA" ExportDate="Sun May 18 13:02:10 2014"
    ExportOptions="DecoratedData ForceProtectedEncoding AllProjDocTrans">

SoftwareRevision is the Logix Designer version that wrote the file. TargetName and TargetType say what was exported; here, a whole controller. ExportDate changes on every export, which matters if you keep exports in version control. Under the root, the components nest like this (abridged):

<Controller Use="Target" Name="Line1" ...>
  <DataTypes> ... </DataTypes>
  <Modules> ... </Modules>
  <AddOnInstructionDefinitions> ... </AddOnInstructionDefinitions>
  <Tags> ... </Tags>                      <!-- controller scope -->
  <Programs>
    <Program Name="MainProgram" ...>
      <Tags> ... </Tags>                  <!-- program scope -->
      <Routines>
        <Routine Name="MainRoutine" Type="RLL">
          <RLLContent>
            <Rung Number="0" Type="N">
              <Comment><![CDATA[Start the conveyor]]></Comment>
              <Text><![CDATA[XIC(Start)XIO(Stop)OTE(Run);]]></Text>
            </Rung>
          </RLLContent>
        </Routine>
      </Routines>
    </Program>
  </Programs>
  <Tasks> ... </Tasks>
</Controller>

Data types are covered in user-defined types and Add-On Instructions in their own article; in the file, both are simply further elements under Controller.

Ladder logic is stored as neutral text

A ladder routine is a Routine element with Type="RLL", containing RLLContent and one Rung element per rung. Each Rung has a Number, a Type, an optional Comment and a Text element whose CDATA holds the logic. Every rung ends with a semicolon, and a branch is a pair of square brackets with commas between the legs:

[XIC(Start_PB),XIC(Motor)]XIO(Stop_PB)OTE(Motor);
XIC(Motor)TON(Fan_Delay,5000,0);
XIC(Part_Eye)ONS(Part_OS)ADD(Parts,1,Parts);

Juxtaposition is series and a bracket group is parallel, so the first rung above reads: (Start_PB or Motor) and not Stop_PB drives Motor. Normal rungs have Type N. The other types the manual lists (I, D, R, IR and pending variants such as rN, e, er and d) mark inserted, deleted, replaced and pending rungs.

Reading neutral text

1756-RM014 lists the neutral text form of every ladder instruction. The operands are positional, which is all you need to read most rungs:

Rockwell's own example from the same manual shows a JSR passing parameters: JSR(DayOfWeek,1,TestDateTime,Test_Result). Instructions that hold state, such as timers, counters and messages, always name a tag of their own type, which is why those tags appear in the export even when you only exported a routine.

Tag data: raw, L5K and decorated

Tag values, module configuration and default values sit in Data elements, which come in three formats. Raw is a hex dump that includes hidden configuration data and is not meant to be read; it is the default and has no Format attribute. Decorated is readable, member by member. L5K is the L5K text format wrapped in CDATA.

On export Logix Designer writes raw and decorated together (except for module InputTag data, which gets no raw form). On import, the formats must appear in the order raw, L5K, decorated, and a later one overwrites an earlier one where they differ. So if you change a value in the decorated data, the decorated value wins. The L5K data format is never exported, only accepted, so that generation tools written for L5K can move to L5X.

Open, import or convert: what to use

File, Open is for an L5X that is a full controller export; that is how 1756-RM014 describes it. A routine, program or rung export goes in through Import, into a project that is already open; when you import a component, select the container it belongs in first (to import a program, select its task). If File, Open refuses a file, look at TargetType in the root element before anything else.

Before you hand-edit an L5X

Editing the XML is legitimate, and Rockwell documents it as a supported workflow. It has consequences that are easy to miss.

• Going online. Importing a full L5X creates a project with a new creation stamp, so it no longer matches a controller downloaded from the original. You must download, or upload into another project; an upload loses whatever the import changed. Component imports and CSV imports that create or retype tags also clear the download stamp.
• Forces. A project imported with forces defaults to Forces Disabled, even if it was exported with forces enabled. Rockwell's instruction is not to modify forces in the file at all.
• Source protection. Since version 20, source-protected routines and Add-On Instructions export encrypted by default. Cleartext needs a workstation enabled for source protection, the 'always encode' option cleared, and the source key in the sk.dat file. Encrypted content sits in an EncodedData element instead of readable logic, so a converter or a reviewer sees nothing of it.
• Comments and booleans. XML comments are allowed anywhere outside a tag and are ignored on import; descriptions are imported. Boolean attributes are true or false in L5X, where L5K uses 1 or 0.
• Data values. Edit the decorated data, not the raw hex, and remember it overrides the raw values on import.

The safe habit is to import every hand-edited file into a scratch project first and check what the import reports before it goes anywhere near the real one.

L5X in version control

Because it is text, an L5X diffs. Committing a full export beside the ACD on every release turns 'what changed between versions' into a readable diff, which is the approach in PLC version control. Expect the root element to change on every export, because ExportDate does, and ignore that line when reviewing.

Converting an L5X to another platform

LADX Convert reads an L5X in the browser and writes the ladder routines as IEC Structured Text, Siemens SCL, Rockwell neutral text or PLCopen XML, with a report of what did not come across. That report is the useful part: instructions it has no equivalent for are left out and flagged for rewriting by hand, routines in other languages are listed as skipped, RTO is flagged where it was read as TON, and tag types it does not model, such as REAL or STRING, are listed rather than silently changed. It does not read L5K; export L5X instead. It does not open an ACD; export from Logix Designer first.

A conversion is a rewrite, so check it. Ladder logic to Structured Text covers the rules and a test sequence for proving the result. For whole-platform moves, see cross-vendor PLC migration and, for older Rockwell systems, PLC-5 to ControlLogix migration.