Alternative PLC Compilers (for Siemens S7 PLC's)?

hcl3646 · Jan 15, 2018

Hi everyone,

I'm pretty new to PLC's in general, and working on a project where I have to get familiar with the PLC compilation process (specifically we will be working with a Siemens S7-1200).

The main issue is that I'm having trouble finding information online about this topic. The most I've been able to find so far is that SCL gets translated to assembly-like STL which turns into machine-comprehensible MC7 instructions.

Are there any alternative or open-source compilers for S7 PLC programs (or just alternative PLC program compilers in general)? I'm hoping that something like this could help me understand the process better.

Also, if anyone can share any information related to how the compilation process works in general for PLC's (assembly, linking) I would greatly appreciate it!

Cheers,
Matt

JRW · Jan 15, 2018

For what purpose?
Manufacturers typically don’t open this knowledge up

JesperMP · Jan 15, 2018

The only info I have ever seen about someone investigating how S7 STL code is converted into S7-1200 IL machine code is this one, in german:
https://www.sps-forum.de/simatic/68502-der-s7-1200-unter-den-rock-geschaut.html

And I have seen that someone succeded in writing a worm that could insert code on the operating system level on S7-1200 CPUs with early firmware. I cannot seem to find that info now (maybe has been removed !?).

Apart from that you wont find a 3rd party compiler for the newer Siemens PLCs S7-1200 or S7-1500. Siemens wont publish the information that would be necessary to create such a 3rd party compiler.

mk42 · Jan 15, 2018

hcl3646 said:
Hi everyone,

I'm pretty new to PLC's in general, and working on a project where I have to get familiar with the PLC compilation process (specifically we will be working with a Siemens S7-1200).

The main issue is that I'm having trouble finding information online about this topic. The most I've been able to find so far is that SCL gets translated to assembly-like STL which turns into machine-comprehensible MC7 instructions.

Are there any alternative or open-source compilers for S7 PLC programs (or just alternative PLC program compilers in general)? I'm hoping that something like this could help me understand the process better.

Also, if anyone can share any information related to how the compilation process works in general for PLC's (assembly, linking) I would greatly appreciate it!

Cheers,
Matt

There generally aren't 3rd party compilers for most PLCs. The Programming software is usually developed especially for the HW, and the compiler gets wrapped up in the middle.

You might have better luck with Codesys for a Raspberry Pi. I don't think it's open source, but because it is on a PI, you might get more visibility into the end result.

JesperMP said:
And I have seen that someone succeded in writing a worm that could insert code on the operating system level on S7-1200 CPUs with early firmware. I cannot seem to find that info now (maybe has been removed !?).

https://www.blackhat.com/docs/us-16...laster-A-Worm-Living-Solely-In-The-PLC-wp.pdf

The paper had some interesting insights, although something like that can be blocked via password protection.

It doesn't look like it goes into the compiler details. I think it simply recorded a Portal download, and then figured out how to store that in a DB to be sent with Tsend/Trecv.

Might be more details if there's a recording of the presentation, vs just the paper.

cardosocea · Jan 15, 2018

Why do you need to be familiar with the PLC compilation process for S7-1200?

I say this because Siemens doesn't, to the best of my memory, use the word compilation in their 1200 or 300 PLC documentation. The only place where I saw that word used was when dealing with PCS7, which doesn't work in the 1200's.

hcl3646 · Jan 16, 2018

Hi, thanks for all the answers! The paper was very interesting and although I don't speak German, I'll look into that too.

To briefly answer the questions some posed, I'm working on a research project looking at possible ways to increase the security around PLC's.

Thanks again.

Alternative PLC Compilers (for Siemens S7 PLC's)?

hcl3646

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JRW

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mk42

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cardosocea

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hcl3646

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