TIA Portal simulation: testing Siemens code without a PLC

TIA Portal simulation means running your Siemens PLC program on a pretend controller on your PC instead of a real one. It's how engineers test code before the hardware arrives, and a way to practise without a controller of your own.

Siemens gives you two main ways to do it, S7-PLCSIM and S7-PLCSIM Advanced, and they're aimed at different jobs. This guide explains what each one does, what it can't do, what to check about licences, and how to practise Siemens code if you don't have TIA Portal at all.

I'm not a Siemens engineer, so I've kept to what Siemens itself says in its documentation and linked every source at the bottom. Versions change often, so if something matters to your project, check the help for the exact version you're running.

What TIA Portal simulation actually means

TIA Portal is Siemens' engineering software. Inside it, STEP 7 is where you configure a controller such as an S7-1200 or S7-1500 and write its program in SCL, LAD, FBD or GRAPH.

Normally you'd download that program into a real controller over a network cable. With simulation, you download it into software that behaves like the controller instead. You can then go online, watch your tags change, and check your logic does what you meant, all without a single piece of hardware.

The key thing to remember is that it's the controller being simulated, not the machine. More on that shortly, because it's the biggest surprise for most people.

S7-PLCSIM: the everyday option

S7-PLCSIM is the simulator most people mean when they talk about TIA Portal simulation. Once it's installed, Siemens' help says the Start simulation option appears in STEP 7 for any device that PLCSIM can simulate. The simulated PLC gets its hardware configuration and program from your project by a normal download, exactly as a real one would.

In practice, the workflow looks like this.

1. Write and compile your program in STEP 7 as normal.
2. Select the controller and choose Start simulation. PLCSIM opens a simulated PLC.
3. Download your project to the simulated controller.
4. Go online and use a watch table to see your tags, or change values to test what happens.

Siemens' current help lists support for S7-1500, S7-1200 and ET 200SP controllers, among others. Exactly which controllers and firmware versions are covered depends on the PLCSIM version, so check the list before you rely on it for an older project.

What PLCSIM doesn't do

PLCSIM is very useful, but it helps to know its limits before you start.

• There's no machine. When your code opens the fill valve, nothing fills. You become the machine, changing input values by hand to pretend a tank is full or a sensor has seen a bottle. For one rule that's fine. For a sequence with timing in it, it gets tedious and it's easy to miss things.
• Some technology functions aren't simulated. For example, Siemens' readme for PLCSIM V20 says it doesn't support simulating S7-1500 motion control technology objects. Each version's readme lists what's missing.
• It's a test tool, not a stand in for real hardware. Real input cards, networks and field devices aren't part of the picture, so some things can only be proven on the real kit.

S7-PLCSIM Advanced: for bigger jobs

S7-PLCSIM Advanced is a separate product aimed at more serious testing. Siemens describes it as a way to test, debug and optimise control programs with digital twins. It creates virtual S7-1500 and ET 200SP controllers on your PC, and reproduces real controller behaviour including communication, safety and web server functions.

It also has a programming interface, so other software can connect to the virtual controller and drive its inputs and outputs. That's what makes it useful for virtual commissioning, where a model of the machine talks to the virtual controller as if it were the real plant.

A few limits are worth knowing.

• It doesn't simulate the S7-1200. For that you need standard S7-PLCSIM.
• It doesn't simulate fieldbus systems such as PROFINET IO and PROFIBUS DP, according to its function manual.
• It's licensed separately from STEP 7.

Adding a process to test against

If you want your simulated controller to have something realistic to control, you need a process model. Siemens' own tool for this is SIMIT, a simulation platform for testing automation projects, commissioning virtually and training operators before a plant goes live. Siemens publishes a getting started guide that combines PLCSIM Advanced, SIMIT and NX Mechatronics Concept Designer for exactly this kind of virtual commissioning.

For a big project, that's a sensible investment. For someone learning, it's a lot of software and licensing to take on just to see a tank fill.

What to check about licences

This is the part that confuses people most, and it has changed between TIA Portal versions, so I won't pretend there's one simple answer. A few questions will get you to the right one.

• Which STEP 7 do you have? Siemens sells STEP 7 Basic, which it calls a price optimised subset, and the fuller STEP 7 Professional. Check which controllers your edition supports.
• Is PLCSIM included with your licence? Look at the scope of delivery for your exact version, or ask your Siemens distributor.
• Do you actually need PLCSIM Advanced? If you only want to test logic for an S7-1500, standard PLCSIM may be enough. Advanced earns its keep when other software needs to connect to the virtual controller.

If you've been given a trial or a starter kit licence, check how long it lasts before you plan a course of study around it.

Practising Siemens code without TIA Portal

If you're learning and don't have TIA Portal, or you want something realistic for your code to control, there's another route.

PLC Gym runs in the browser. You can write in all four Siemens languages it supports, SCL, LAD, FBD and GRAPH, and run your program against a working 3D process rather than a watch table. A tank actually fills. A pump actually runs down. Automatic tests then check every rule in the job.

It's honest to say what it isn't. It's not TIA Portal, and our language reference lists the assumptions it makes and where it differs from the real software. It's a place to learn and practise the logic, so that when you do sit down in TIA Portal, the code is the easy part.

If you want to try it, these are good first steps:

• The first mission gets you writing your first line and watching a tank respond.
• Signal scaling turns a raw sensor reading into a level you can use, in FBD.
• The batch sequence runs a process through four phases in GRAPH or SFC.

Our Siemens PLC training puts all of that in order, from your first scan to complete sequences.

Which should you use?

Here's the simple version.

1. You're learning the logic. A browser simulator with a built in process is the quickest way to see cause and effect.
2. You're learning TIA Portal itself. Use TIA Portal with S7-PLCSIM, so you get used to the real menus and workflow.
3. You're testing a real project before site. Use PLCSIM for your exact controller and firmware, and test every rule you can.
4. You're doing virtual commissioning. Look at PLCSIM Advanced with a process model such as SIMIT.

If you'd like the wider picture of how emulators and simulators differ, including Rockwell's options, our guide to PLC emulators covers it. And if Structured Text is new to you, the Structured Text guide is written with Siemens SCL in mind.

Sources

• S7-PLCSIM help, Siemens
• S7-PLCSIM V20 readme, Siemens
• S7-PLCSIM Advanced, Siemens
• S7-PLCSIM Advanced function manual, Siemens
• STEP 7 in the TIA Portal, Siemens
• SIMIT, Siemens
• Virtual commissioning of machines with S7-PLCSIM Advanced, SIMIT and NX MCD: getting started, Siemens