Modernization Doesn't Have to Be Overwhelming - but it Often Feels That Way.

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With the rapidly changing automation hardware and software landscape the word modernization can be a bit overwhelming on its face, but if you break it down into more manageable and achievable components, it can be more easily achieved for all those involved with a lesser exposure to risk.

Having been involved in this process for over 30 years, there are a few common threads. No one wants to be forced to “upgrade” their systems just because there is a new product available. Unless that new product offers a feature that is desired by the user of course. In most cases, the inability to purchase hardware components from the manufacturer is a substantial driver for the modernization discussion. Cost is less of concern but can play a role as well. In addition to the hardware and software migration, the drawings should also be updated to properly support the new system moving forward so that the service personnel can properly troubleshoot the system as needed after the migration.

With many customers, their systems are up and running making product, so the prospect of stopping production for any reason seems unnecessary or out of the question. This is of course, until the production stops due to an issue relating to the hardware components in the system, then the “money is no object” philosophy prevails. Waiting for that day to come seems a bit risky but it seems to happen fairly often, as opposed to the planning for a more proactive approach to the “soon to be” crisis.

PLC Components Involved in this Process



The controllers and associated IO modules may or may not be currently operating on a Fieldbus system of some sort. From the Siemens perspective, the S7 300 controllers have been around since 1995 along with the old tried and true Profibus serial RS485 fieldbus technology. We are talking about a 30-year-old platform that has performed across multiple industries for many years. And like most systems, technology and innovation sometimes demand a change that the older systems were never designed for. Say nothing about the ease of configuration and programming of the newer platforms. Siemens uses a product lifecycle management policy which provides module status throughout the lifecycle of their products. PLM, as it is called, has a defined timeline that is followed to ensure customers have ample time to make decisions for their systems, both as new and legacy systems. Below is an example of the HMI PLM from Siemens for reference.

Currently, the S7300 product and its IO modules have been placed in the PM400 “phase out” status as of October 1st 2023. The discontinuation PM410 went into effect on October 1st 2025, so you can typically no longer purchase new components. Most of the components are considered spare parts and are sold as such. The other option is repair/replace which in any case will require the old module to be returned as part of the replace process. The PM410 will remain until about October 1st 2033. As a note, the ET200S distributed IO product reached the PM410 milestone on October 1st 2023. The following URL will provide additional information regarding possible replacement S7300 components from the S7 1500 hardware catalog. https://support.industry.siemens.com/cs/us/en/view/109809890.

The ET200SP is the successor to the ET200S product. In case you are wondering, the ET200SP is not interchangeable with the older ET200S at the component level. The entire IO rack must be replaced.

System with a PLC and Distributed IO on a Profibus Network

So, let’s consider a typical system with a PLC and distributed IO on a Profibus network. You have a few options available to you. But before you start, you should make sure that you have the actual project that is currently running in the S7 300 CPU. Performing a compare with SIMATIC Manager can verify that is the case. If not then you can copy the blocks that do not match from the online clocks folder to the offline blocks folder before proceeding with the process. If you do not have an offline copy of the project and you decide to upload the system to SIMATIC manager, understand that there are no symbols or comments available in the S7300 controller that can be uploaded. Any symbol names in the data blocks are also not available. You will be starting with an undocumented program which is possible but not preferred by any means.

One option is to replace the ET200 IO with the Profibus equivalent in the new IO product family. Leaving the CPU in place for now. This allows a piece by piece approach to modernization and creates some quantity of spare modules of the older type. The typical S7 300 system was programmed with STEP 7 using the SIMATIC Manager which is still an active product, and in most cases, can support the ET200SP/ MP modules in SIMATIC Manager. The older ET200M, based on S7 300 modules, is now the ET200MP based on the S71500 modules. The current ET200SP is the replacement for the old ET200S. This solution is not the best long-term solution due to the age of Profibus technology, but it can be implemented with existing network infrastructure. If your system happens to be an S7400H, please note that there are no redundant Profibus interface modules in the new ET200MP as compared to the old redundant ET200M units. That would be a case where upgrading both of the S7400H CPU’s to a Profinet capable unit and using one of the available redundancy options Siemens offers like MRP(Media Redundancy Protocol) or S2 redundancy shown below which works without additional hardware. The IO devices must support S2 redundancy however.

If your current CPU also has a Profinet port, or a newer CP card that can act as a Profinet IO controller, you could replace the older Profibus based devices with a more modern flexible Ethernet solution using Profinet as your fieldbus technology creating a new foundation for your automation system. This will involve Ethernet cabling to be run but the PLC program will typically remain unchanged because the IO addresses of the Profibus modules can be reused in the new Profinet system. The only issue is the addresses that are assigned to the old modules cannot be duplicated by the new modules in the hardware configuration. That is where having a backup copy as a reference is an invaluable resource. Also understand that as long as your controller will support both Profibus and Profinet, you can have a mixed system in operation while you are in the process of system modernization. This is a more manageable piece by piece approach for modernization. At some point however, in the not too distant future the Profibus components will be going the way of the S7 300 components simply due to a diminishing demand for Profibus technology components as compared to Ethernet based Profinet components. Out with the old and in with the new is more than likely to occur.

The S7300 system was developed using SIMATIC Manager, and is still an active product for engineering. The migration to TIA Portal is also possible to move away from the SIMATIC Manager if desired. The STEP7 hardware configuration should be exported to a .cfg file then can be evaluated by a tool called the TIA Readiness Tool that can be found at the following link. https://support.industry.siemens.com/cs/ww/en/view/60162195

The readiness tool can evaluate the .cfg file and provide a report of the modules that are and are not supported in TIA Portal software. Typically, any module released after about 2009 will be supported in the hardware catalog of TIA Portal. If a module is not supported then you must decide what actions must be taken. If the S7300 is being replaced by the S7 1500 then updating the S7300 modules in your SIMATIC Manager hardware configuration will then allow the migration from SIMATIC Manager to TIA Portal to proceed. From a module perspective, there are a number of modules that are not supported in the TIA Portal hardware catalog. They are typically the FM (Function Modules) in the S7300. Cam, Stepper, and Servo modules are examples of modules that will not migrate to TIA portal. Any system with those modules must be re-engineered in TIA Portal using the current components required to solve the automation task that the old FM modules performed. So, excluding the FM modules, the end result is an S7 300 system in TIA Portal software, which is step 1 of the 2-step process. In SIMATIC manage, the software must also be consistent. That involves a right mouse on the blocks folder and selecting the “Check Block Consistency”. That will allow you to recompile all the blocks in your STEP 7 project. After compiling without errors, the *.S7p file can be migrated from STEP 7 to TIA Portal using the Migrate Project function in TIA Portal. You can include the STEP 7 hardware if you wish. Then once you have the S7300 system in TIA portal, you can migrate to an S7 1500 using the migration tools integrated in TIA Portal. The source S7 300 in TIA Portal will still exist after the migration and will provide a valuable reference during the engineering process. The S71500 modules will have to be manually inserted into the project based on the S7 300 module capabilities but all the program components will now be suitable for the S7 1500 depending on the structure of the source code of course. Then you can load the project into the S71500 and test. If for some reason the system needs to be returned to its original state, just put the old S7 300 back in the system. The MMC in the S7300 will still be the old system. Managing the program on the S7300 MMC requires a prommer that is either built into the PC like the Siemens MD57A or a USB connected prommer. The MMC cannot be managed by Windows. Windows can only format the MMC which will render is useless for further use in the S7 300 CPU’s. Purchasing a new MMC for the S7300 is an option if you do not have access to a prommer. That will allow the S7300 Program to be loaded into the S7 300 system using TIA portal if your goal is just to use TIA Portal with your S7 300 system. The original loaded project from SIMATIC manager is unchanged on the old MMC.

A lot of which way to proceed is going to be based on the amount, if any, of distributed IO in the system because running Ethernet cables may or may not be an easy task in your existing system. I would mention that most if not all newer systems take advantage of the capabilities offered by an Ethernet based system due to all the devices and capabilities offered in a modern Ethernet based system.

Mike Davis

MODERNIZATION DOESN'T HAVE TO BE OVERWHELMING - BUT IT OFTEN FEELS THAT WAY