Ian Caddy ianc at goanna.iinet.net.au
Fri May 14 01:23:08 UTC 2010

On 14/05/2010 9:09 AM, Joel Sherrill wrote:
> On 05/13/2010 08:03 PM, Ian Caddy wrote:
>> Hi Aaron,
>> On 14/05/2010 6:40 AM, Aaron J. Grier wrote:
>>> this is a long-shot, but has anybody out there done any investigation of
>>> implementing IEC 61131(-3) on RTEMS to create a programmable logic
>>> controller? RTEMS seems like it would be suitable to handle both a
>>> hard-real-time PLC loop in addition to human-machine-interface duties.
>> We have used RTEMS for a number of years in a Remote Terminal Unit (RTU)
>> based product (for Supervisory Control and Data Acquisition - SCADA)
>> that also contains IEC61131-3 functionality. In an RTU device the
>> reporting (communications) of time based eventing is more important than
>> the logic running in the unit so it is a bit different to a PLC type
>> device but RTEMS had no problems performing admirably with this.
>> We run the logic as a task with a certain priority in the system.
>> The 61131-3 system that we use is quite old and was bought in from
>> IsaGRAF but works OK.
>> Let me know if you have any more specific questions.
> Do you know of any free software projects that relate
> to this and might make sense to port to RTEMS?

The 61131-3 contains two elements, there is a graphical front end which 
needs to implement the 5 programming languages of the standard which are:

Function Block Diagrams
Structured Text
Ladder Logic
Sequential Function Charts
Instruction Lists

then in the embedded device is the logic execution engine to execute the 
coded instructions.

One of the things we have been looking at is replacing that with 
something else on a newer product, although I haven't check their 
licensing, which could be GPL.

Beremiz is a framework for automation, which contains a number of pieces 
including IEC61131-3 functionality:


This in turn uses a number of different pieces to make a complete 
system, such as the PLCOpen Editor, an IEC compiler.

Information on the OpenPLC group can also be found at:



Ian Caddy

Ian Caddy
Goanna Technologies Pty Ltd
+61 8 9444 2634

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