Upgrading S7-1500 CPU Firmware V2.5 to V2.6 in TIA Portal V15

Overview

The SIMATIC S7-1516-3PN (article number 6ES7 516-3AN01-0AB0) ships in multiple firmware versions. A common engineering scenario is a project created in TIA Portal V15 that targets firmware V2.5, while the physical PLC on the shop floor has been flashed to V2.6 — or vice-versa. Engineers frequently download the firmware file 6ES7 516-3AN01-0AB0 V02.06.00.upd from the Siemens support site and try to use it to change the firmware version inside the offline TIA Portal project. That approach does not work: the .upd file is a CPU-side firmware image, not a TIA Portal project upgrade utility.

This article explains what the .upd file actually does, why TIA Portal V15 cannot represent V2.6 in its hardware catalog, and three concrete paths to make V2.5-to-V2.6 migration safe and repeatable.

Understanding the Firmware / TIA Portal Relationship

Each TIA Portal release supports a defined set of CPU firmware versions. The relationship is not bidirectional:

• TIA Portal → Firmware visibility: The hardware catalog exposes only firmware versions that the TIA Portal release knows about. Older firmwares are listed, newer firmwares are not.
• Firmware → TIA Portal compatibility: A newer firmware on the CPU generally remains downloadable from older TIA Portal projects, but new instructions, new data types, or new HMI options introduced in the newer firmware become invisible.

For the S7-1500 family, TIA Portal V15 covers firmware up to V2.5.x. Firmware V2.6 (released in 2017/2018) requires TIA Portal V15.1 or later as the engineering environment. The official Siemens knowledge base entry Firmware update S7-1500 CPUs incl. Displays and ET 200 CPUs states that "when firmware is updated, it must always be updated to the latest version available for the relevant article number."

What the .upd File Actually Does

The .upd file you downloaded from Siemens is the CPU firmware image. It is consumed by the PLC, not by TIA Portal. The PLC accepts the .upd file in three ways:

1. Online via TIA Portal: Online & Diagnostics → Functions → Firmware update. The .upd is transferred to the running CPU, which then reboots into the new firmware.
2. Via SIMATIC Memory Card: The .upd is placed in the FWUPDATE folder on the SIMATIC MC and the CPU is power-cycled.
3. Via SIMATIC Automation Tool: Bulk firmware update across multiple PLCs on a subnet.

None of these mechanisms modify the offline TIA Portal project. The project is a developer-side artifact; the .upd is a target-side artifact. Conflating them is the most common reason engineers get stuck.

Prerequisites

Regardless of which path you choose, prepare the following before touching firmware or TIA Portal:

• Project backup: Archive the current TIA Portal project (Project → Archive) and the SIMATIC Memory Card contents.
• PLC backup: Perform Online → Backup from online device in TIA Portal, or read the full PLC into the project. This captures the live DB values, retentive tags, and the current program.
• Network access: Confirm the engineering station can reach the CPU over PROFINET. Firmware updates require HTTPS or TIA Portal online protocols (TCP/102, TCP/443 depending on configuration).
• CPU operating mode: Plan a stop window. Firmware updates force the CPU to STOP, lose any non-retentive process data, and reset diagnostic buffers.
• Power supply: Use a UPS or secure mains. A power loss mid-firmware-update can leave the CPU in an unrecoverable state, requiring a memory-card-based recovery.
• Article number match: Verify the .upd filename ends with the same article number as the PLC's MLFB plate (here 6ES7 516-3AN01-0AB0). Loading an .upd for a different hardware revision will be rejected by the CPU.

Path A — Install TIA Portal V15.1 in Parallel (Recommended)

This is the only path that gives you V2.6 in the offline project, full V2.6 instruction support, and a clean hardware catalog. Siemens explicitly allows V15 and V15.1 to coexist on the same engineering station under specific conditions.

Step-by-Step

1. Close TIA Portal V15.
2. Run the TIA Portal V15.1 installer. Select a different installation directory than V15 (default C:\Program Files\Siemens\Automation\Portal V15.1).
3. When prompted for licensing, choose to migrate the V15 license. The V15 license is valid for V15.1; you do not need a new license key.
4. When prompted for SIMATIC WinCC Professional, do not install WinCC Professional into the parallel V15.1 instance. WinCC Professional has known conflicts with parallel installations and is the reason Siemens restricts parallel setup.
5. Complete the V15.1 installation, including any required HSPs for your I/O.
6. Open the V2.5 project in TIA Portal V15.1. TIA Portal will perform an automatic project upgrade.
7. Open the device configuration of the S7-1516-3PN, then in the Properties → General → Catalog dropdown change the firmware selection from V2.5 to V2.6.
8. Compile (hardware + software) and save the project as a new archive.

Verification

• The device properties show Firmware version: V2.6.
• Hardware diagnostics report no compatibility errors.
• The S7-1516-3PN module now appears in the TIA Portal V15.1 catalog under V2.6.

Path B — Keep Mismatched Versions (V2.5 Project, V2.6 PLC)

Many production environments deliberately run with the project on V2.5 and the physical CPU on V2.6. TIA Portal V15 can still compile, download, and go online against a V2.6 CPU as long as the V2.5 project does not use instructions or data types introduced after V2.5.

When This Is Safe

• The V2.6 firmware is a maintenance release that does not deprecate V2.5 instruction set.
• No new V2.6 instructions or data types are referenced in the user program.
• The CPU is in RUN, and a download must not interrupt production.

How To Download

1. Connect to the CPU with TIA Portal V15.
2. Right-click the S7-1516-3PN → Download to device.
3. TIA Portal will detect the online firmware (V2.6) and the offline project firmware (V2.5). It will warn you about the mismatch but allow the download.
4. Confirm the download. The PLC may transition through STOP → RUN depending on what is being loaded.

Path C — Flash the PLC Firmware Separately (No Project Change)

If your goal is simply to bring an older fleet of PLCs to V2.6 without re-engineering the TIA Portal project, perform the firmware update on the physical CPU only.

Method 1 — Online via TIA Portal (Single PLC)

1. Open the project in TIA Portal V15.
2. Select the S7-1516-3PN → Online & Diagnostics.
3. Navigate to Functions → Firmware update.
4. Browse to 6ES7 516-3AN01-0AB0 V02.06.00.upd.
5. Select the CPU, click Run update.
6. The CPU enters STOP, transfers the firmware, then performs a restart.
7. After the restart, verify in the online diagnostics that the firmware version reads V2.6.

Method 2 — Via SIMATIC Memory Card (Offline / No TIA Required)

1. Power down the CPU.
2. Remove the SIMATIC Memory Card.
3. Insert the card into a card reader on the engineering station.
4. Create the folder structure FWUPDATE\S7300 on the card (this directory is shared between S7-300/400/1500 firmware files).
5. Copy 6ES7 516-3AN01-0AB0 V02.06.00.upd into FWUPDATE\S7300.
6. Reinsert the card into the CPU.
7. Power on the CPU. The CPU detects the .upd file, runs the update automatically, and deletes the file after a successful flash.

Method 3 — SIMATIC Automation Tool (Bulk Update)

For multi-PLC rollouts, the SIMATIC Automation Tool can distribute the .upd file across a subnet and trigger the update from a single operator action. The tool is free to download from Siemens support and uses the same TIA Portal online protocol for transfer.

Download Behavior: PLC Stop, DB Initialization, and STOP-to-RUN Transition

Understanding the runtime behavior of a firmware-mismatch download prevents surprises on a running process.

The download dialog in TIA Portal explicitly warns the engineer when DBs will be re-initialized with their start values. Heed this warning in production environments — schedule the firmware migration during a maintenance window if process-critical data blocks are non-retentive.

Verification and Commissioning Checks

After completing any of the three paths, run the following validation sequence:

1. Online diagnostics: Online & Diagnostics → Diagnostics → General. Verify firmware version displays V2.6 and the CPU is in RUN with no diagnostic buffer entries dated after the update.
2. Compare offline / online: Online → Compare offline / online. If using Path A, expect zero structural differences. If using Path B, expect the firmware-version mismatch warning.
3. Watch table smoke test: Load the existing watch tables and force-check critical tags for response and correct values.
4. HMI connection test: If WinCC Comfort/Advanced or a third-party HMI is bound to the PLC, verify the HMI connection still establishes and live tags update.
5. Retentive data audit: Cross-check the PLC properties → Retentive memory settings. Confirm all required tags are marked retentive before the next power cycle.
6. Backup the final state: Online → Backup from online device. Archive the post-migration project plus the new backup.

Field-Proven Caveats and Edge Cases

• HSP vs. TIA version: A Hardware Support Package (HSP) downloaded separately does not unlock firmware versions that are post-TIA-version. For example, the V15 HSP catalog still cannot represent V2.6 because V2.6 was released after V15 was frozen. You must upgrade the TIA Portal itself.
• WinCC Professional conflict: Attempting to install WinCC Professional in both V15 and V15.1 on the same machine will fail the parallel install. Use V15.1's WinCC Professional and back-migrate only if you must keep V15 for one specific project.
• Multi-user / TIA Project Server: If your project lives on a TIA Project Server, check the server's TIA Portal version. Concurrent engineering with mixed TIA versions on the same server is restricted.
• Firmware downgrade: Siemens firmware updates are typically one-way. Downgrading from V2.6 to V2.5 is not supported by the .upd file alone; you must use a SIMATIC Memory Card with a factory-reset workflow to restore older firmware. Reference the Siemens knowledge base article 109478459 for downgrade procedure details.
• Article number drift: Siemens has released 6ES7 516-3AN00-..., ...3AN01-..., and later revisions. Each article number has its own .upd lineage. Do not cross-load .upd files between revisions — the CPU rejects them.
• Fail-safe CPUs: For S7-1516F-3PN, additional F-CPU signature and F-activation steps apply before firmware changes. Validate the F-signature is preserved through the update.
• Display and ET 200SP CPUs: The same firmware-update entry also covers the SIMATIC ET 200SP CPU and ET 200pro CPU families. If your topology includes distributed ET 200SP CPUs, plan a coordinated update window.

Cross-Platform Note: Other Vendors

Although this article focuses on Siemens, the firmware / engineering-tool separation pattern is industry-wide. For example, AutomationDirect's Productivity 2000 series uses a similar firmware-version-locked-to-engineering-version model — the P2-550 firmware history shows that fixes such as "P2-CPU Goes to RUN immediately after E01005 occurring instead of forcing to STOP" are tied to specific firmware versions and require matching programming-software versions. The engineering rule is the same: confirm your engineering tool can see the firmware your hardware is running before you attempt a download.

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