Siemens S7-300 PLC Programming

Do you operate a production line based on proven Siemens S7-300 controllers?
Are you looking for experts who not only understand modern automation solutions, but can also professionally diagnose, modify, or modernize legacy Siemens PLC systems?
We have many years of experience in programming Siemens S7-300 PLCs. We specialize in restoring the full performance of legacy control systems and seamlessly integrating them with new technologies.

Why entrust us with S7-300 PLC programming?

For many years, S7-300 controllers formed the backbone of industrial automation. Today, they require specialized expertise that many younger programmers simply do not possess. Over the years, we have programmed S7-300 controllers for large companies in the automotive, foundry, and transportation industries. Now, we bring this knowledge and experience to support your project.

Your safety is our standard — not an optional extra

We understand that the stability of your production and machine operation cannot depend on a single individual.

100% in-house programming team: Unlike companies relying on subcontractors, the core of Amister consists of permanent employees. You can be confident that your PLC programmer will not disappear halfway through the project, and that critical know-how will remain within your organization for years to come.

Redundancy system (Backup Procedure): Each S7-300 project is assigned both a project leader and an equally qualified backup engineer. Unexpected events on our side never translate into downtime on yours.

No juniors on the front line: Only proven experts are assigned to your S7-300 controller. Every junior engineer completes an intensive three-month training program before supporting an expert on live production systems.

No Ambiguities. No “hidden costs.”

Precision is critical when modernizing Siemens S7-300 controllers. Our project process is designed so you can focus on your business with complete peace of mind.

Single Point of Contact: You don’t need to coordinate with multiple programmers. You work with one dedicated Team Leader who manages the entire project and reports progress transparently.

Clearly defined project scope: Before a single line of code is written, we jointly define the scope of work. This protects your budget from unpleasant surprises during implementation.

Transparent billing: Whether you choose a Fixed Price or Time & Material model, you always know exactly what you are paying for. Progress reports are delivered regularly — not only together with the invoice.

Quality guarantee: Our implementations result in stable, fully functional production lines and machines. Our effectiveness is confirmed by references from leading industry players.

A partner who understands your business

By choosing Amister, you partner with a company built on solid foundations.

Barrier-free communication: Our engineers are fluent in English and German — a key advantage when delivering projects for international corporations (e.g. BMW, Škoda, Mercedes).

Experience measured in years: Most of our engineering team has been with us for over five years. This means deep, hands-on expertise in Siemens S7-300 systems.

Financial stability: We are an organically growing company, managed based on profitability rather than external funding. You eliminate the risk of your system integrator failing during your investment.

Our technology workshop for Siemens S7-300 PLCs:

STEP 7 (Classic) V5.x environment

Full support for projects where TIA Portal is not a viable solution. Diagnostics, code modifications, and optimization of program blocks.

Migration to TIA Portal

Where the controller hardware allows it, we migrate legacy projects to a modern engineering environment, laying the groundwork for future hardware upgrades.

Profibus & MPI communication

Expert configuration of legacy communication networks, ensuring stable and reliable data exchange between the CPU, I/O islands, and HMI panels.

WinCC Flexible visualization

Maintenance and development of HMI interfaces for OP/TP series panels, fully compatible with Siemens S7-300 controllers.

Integration with modern systems

We bridge the gap between legacy and modern automation — integrating S7-300 PLCs with S7-1200 / S7-1500 controllers via communication gateways or PROFINET networks.

Diagnostics and support

We rapidly diagnose issues in existing S7-300 control systems. Our team supports the replacement of faulty I/O modules and CPUs, ensuring minimal production downtime.

Looking for Siemens S7-300 PLC programming specialists?

Expert knowledge of programming languages for S7-300

In S7-300 projects, proficiency in programming languages that are rarely used in their pure form in newer PLC platforms is essential.

Statement List (STL / AWL)

Many legacy S7-300 programs are based on instruction list logic. We are able to read, debug, and optimize this low-level code — a skill that is increasingly rare on today’s market.

Ladder Diagram (LAD)

We create clear, readable ladder logic that simplifies troubleshooting and maintenance for your maintenance teams.

Function Block Diagram (FBD)

We build modular, well-structured programs based on proven and reusable function libraries.

S7-SCL (Structured Control Language)

Ideal for complex mathematical calculations and advanced data processing within Siemens S7-300 systems.

Does your S7-300 controller need expert support?

Don’t risk unplanned downtime — rely on proven experience with SIMATIC Classic systems.

S7-300 Modernization & Retrofit

You don’t need to replace an entire machine to gain new functionality. As part of our Siemens S7-300 PLC programming services, we offer:

Code audit

We assess the condition of your software and identify bottlenecks, risks, and optimization opportunities.

Backup & security

We protect your know-how by creating up-to-date, secure backups of your PLC programs.

Migration planning

If the S7-300 no longer meets your requirements, we design a safe and structured migration path to S7-1500, minimizing production downtime.

Trust confirmed by comprehensive knowledge of industrial programming standards.

BMW TMO

Daimler Integra

Daimler Powertrain

GSC

VASS

Industries where S7-300 still forms the backbone of production

Although Siemens promotes newer platforms, SIMATIC S7-300 controllers remain the “heart” of thousands of industrial plants worldwide. Their legendary durability and widespread installed base mean they still control critical production processes. We understand the challenges of maintaining systems that have been operating reliably for decades and provide support tailored to the specific requirements of your industry.

Automotive Industry

In an industry where every second of cycle time matters, Siemens S7-300 controllers still drive thousands of welding stations, assembly lines, and overhead conveyor systems.

Standards compliance: We have unique expertise in programming according to VASS, Integra, and TMO (BMW) standards.

Adaptations for new vehicle models: We support retooling and adaptation of existing lines for new vehicle models — without the need for costly replacement of the entire PLC infrastructure.

Network diagnostics: We diagnose and resolve issues related to Profibus, Profinet, and MPI networks, eliminating downtime caused by communication faults.

Machine Builders (OEMs)

Many machines delivered 10–15 years ago are still in operation at end customers’ sites. As your technology partner, we ensure their continued reliability.

Service & diagnostics: We support troubleshooting and servicing of machines based on Siemens S7-300 controllers.

Modernization (Retrofit): We design and implement upgrades from legacy HMI panels to modern Comfort or Basic panels while retaining existing S7-300 PLCs.

Performance optimization & expansion: When machines require higher throughput, we optimize STL/LAD code and add new functions and process steps by appropriately extending the Siemens PLC program.

Chemical & Heavy Industry

In harsh environments with high process continuity requirements, the S7-300 is valued for its robust hardware design.

Process safety: We support Fail-Safe systems (S7-300F), ensuring the correctness and reliability of safety-related algorithms.

Distributed I/O systems: We manage complex architectures based on ET200M remote I/O stations, maintaining stable communication between field islands and the main control cabinet.

SCADA data migration: We integrate legacy PLCs with modern SCADA systems for reporting and data archiving, providing real-time visibility into process parameters.

Food & Beverage Industry (F&B)

High production dynamics and frequent recipe changes require a flexible approach to legacy PLC code.

Line integration: We connect machines from different manufacturers — often based on S7-300 controllers — into one coherent production system.

HMI modernization: We migrate visualization from obsolete OP panels (often no longer readable) to modern touchscreen solutions, improving operator ergonomics.

Recipe management: We expand data blocks and control functions to support a larger number of product variants on the same production line.

Selected S7-300 PLC Programming Project Examples

Relocation and Modification of Assembly Machines – MDC Power (Mercedes-Benz), Arnstadt

Project objective: Recommissioning of three Bayer assembly machines following relocation and technical modifications.

Use of S7-300: The machines were equipped with a total of three Siemens S7-300 PLC controllers.

Scope of work The project covered: crankshaft bridge assembly station, technological bore plugging station, engine block leak testing station.

Technologies: In addition to Siemens S7-300 PLCs, the project involved approximately 50 SINAMICS S120 servo axes, KUKA robots, NeuroCheck vision systems, and integration with the PRISMA higher-level control system.

more information

Implementation of New Product Types – Škoda Auto, Mladá Boleslav

Project objective: Adaptation of existing cylinder head assembly lines and engine block lines to support new engine types in 2024–2025.

Use of S7-300: Control systems were based on Siemens S7-300 PLCs, with programming carried out using SIMATIC Manager and WinCC Flexible.

Scope of work: PLC software modifications to accommodate mechanical and electrical changes while maintaining support for existing product variants. Selected stations were also migrated to newer PLC platforms, including program adaptation following replacement of legacy control units.

Technologies: The project included advanced press-fit processes (Bayer, Kistler), adhesive dispensing systems (DreiBond), leak testing systems (Bayer DLP), and integration with the IMIS manufacturing execution system.

more information

Clients and locations where we have implemented projects

Star Assembly SRL

Sebeș, Romania

Audi

Gyor, Hungary

BMW

Steyr, Austria

Stellantis

Mirafiori, Italy

BMW

Dingolfing, Germany

Daimler

Brühl, Germany

NIDEC

Niepołomice, Poland

Skoda

Mlada Boleslav, Czech Republic

Liebherr

Bischofshofen, Austria

Festo

Budapest, Hungary

Daimler

Untertürkheim, Germany

Dana

Amal, Sweden

Looking for a Siemens S7-300 PLC specialist? Contact us today!

Frequently asked questions (FAQ) – Siemens S7-300 PLCs

Is Siemens still supporting S7-300 controllers?

The S7-300 family is currently in the phase of being phased out (Product cancellation/Legacy status). This means that new units are becoming increasingly difficult to obtain and more expensive, as the manufacturer is gradually reducing their mass production.
Nevertheless, we continue to offer comprehensive services in this field. Our specialty is Siemens S7 PLC programming, through which we provide full support for existing systems, maintenance of current applications, and assistance in selecting spare parts. If you are planning a plant modernization, we will prepare a secure migration plan to the modern S7-1500 series for you.

Do you program in STL (AWL)?

Yes — this is one of our core competencies. Many legacy S7-300 programs are heavily based on Instruction List (STL/AWL). We can read, diagnose, optimize, and develop new functionality in STL, which is essential when servicing machines that are 10–20 years old.

Can an old S7-300 PLC be connected to a modern HMI panel?

Absolutely. We deliver HMI Retrofit projects, replacing obsolete or damaged panels (e.g. OP or TP series) with modern Comfort or Basic panels. Communication is configured to ensure seamless cooperation with the existing S7-300 PLC.

Is migration from S7-300 to S7-1500 required right now?

Not always. If your machine operates reliably and spare parts availability is secured, we can focus on optimizing the existing code. Migration is recommended when production expansion is planned, critical spare parts are unavailable, or technical documentation and backups are missing.

Do you have experience with VASS / Integra standards?

Yes. We have hands-on experience with automotive standards used by major OEMs such as Volkswagen, Mercedes-Benz, and BMW. We understand block structures, naming conventions, and safety (Safety) requirements essential for these standards.

Can you help if the PLC program has been lost?

Yes. We support program recovery (if the PLC is not password-protected) and create professional backups. If documentation is missing, we can perform logic reconstruction based on physical wiring analysis and machine behavior.

Can S7-300 communicate with modern drives via PROFINET?

Yes. Despite being a legacy platform, many S7-300 CPUs (especially PN/DP versions) operate reliably in PROFINET networks. We integrate S7-300 controllers with modern SINAMICS drives, servo systems, and vision solutions.

Which engineering environments do you use for S7-300 programming?

Depending on hardware version and project requirements, we work with:
– STEP 7 Classic (SIMATIC Manager V5.x) – for legacy installations requiring original project structure.
– TIA Portal – for newer S7-300 CPUs that support migration to a modern engineering environment.

Do you support modernization of older S7-300-based systems?

Yes. We support:
– Replacement of damaged PLC units with newer S7-300 models,
– Full migration to S7-1500 while preserving existing electrical infrastructure (e.g. using I/O adapters),
– Safety system upgrades.

Which programming languages do you use for S7-300?

We are fluent in:
– LAD (Ladder Diagram) – for clarity and ease of maintenance,
– STL (AWL) – critical for S7-300; advanced low-level debugging and development,
– FBD and SCL – for data processing and complex calculations.

Do you also design HMI / SCADA visualization?

Yes. We design intuitive and modern user interfaces using:
– WinCC Flexible / WinCC Classic – for legacy OP/TP panels,
– WinCC TIA Portal – for modern Comfort and Basic panels. We provide clear diagnostics that significantly reduce machine downtime.

Do you offer post-project support?

Yes. We don’t leave you with just the code. We offer:
– Production start-up assistance,
– Training for Maintenance teams in S7-300 diagnostics,
– Ongoing technical support and regular software backups.

Contact us – we’ll respond within 24 hours!

Do you have questions about Siemens S7 PLC programming? Fill out the contact form, and our team will get back to you within 24 hours – either by phone or email.

During the conversation or correspondence, we will define the scope of work and services you are interested in. Then, we will conduct an internal analysis of your inquiry to prepare the best possible solution.

Within a maximum of 5 business days, we will get back to you with information on the next steps.

Take the step towards modern automation – fill out the form now!

Jakub Urbańczyk

Vice-president