S7-1200 CPU 1215C 6ES7215-1BG40-0XB0: Decoding FS 12 and Resolving TIA Portal V18 Firmware 4.6.1 Mismatch

The SIMATIC S7-1200 compact CPU with MLFB 6ES7215-1BG40-0XB0 is one of the most widely deployed controllers in the S7-1200 family. The two-letter suffix BG40 identifies the AC/DC/Relay variant (120/230 V AC supply, 24 V DC logic, relay outputs) and the trailing 0XB0 denotes the standard production grade with no conformal coating. When this CPU is purchased on the secondary market, two markings frequently confuse first-time users: the firmware version reported by the device and the hardware FS (Functional State) number printed on the front label. This article decodes both, explains why a TIA Portal V18 project may refuse to download to a CPU flashed with firmware V4.6.1, and provides a deterministic field procedure to bring the device back into a usable state.

1. Hardware Identification and Functional Specification

The 6ES7215-1BG40-0XB0 is the catalog identifier for the SIMATIC S7-1200, CPU 1215C, compact CPU, AC/DC/Relay. The two integrated PROFINET interfaces (X1, X2) are physically separate Ethernet ports. Key technical figures for this MLFB are summarized in the table below.

The full device catalog entry is published on Siemens Industry Mall: 6ES7215-1BG40-0XB0 — CPU 1215C AC/DC/Relay. The wiring diagram (terminal assignments for the AC line, 24 V sensor power, digital inputs, and relay contacts) is published in the S7-1200 manual collection: CPU 1215C wiring diagrams (TIA documentation portal).

2. What "FS 12" Actually Means

FS stands for Functional State (sometimes written F-State in English documentation). It is Siemens' internal release state counter for the hardware of a SIMATIC module. Each time a hardware revision is released for production that adds, removes, or alters the externally visible function set of the device, the FS number is incremented.

The relationship between FS and the user-visible product is roughly equivalent to a hardware revision letter on a non-Siemens device. The following points are field-proven and are not marketing copy:

• FS describes the hardware, not the firmware. It is printed on the label and does not change when you update firmware.
• Newer FS levels generally mean a more recent hardware production run, which can include engineering fixes, component second sources, or new features that are only fully supported with a matching firmware.
• FS values do not map 1:1 to firmware versions. A CPU with FS 12 may have shipped with firmware V4.1, V4.2, V4.3, V4.4, V4.5, or V4.6, depending on the production date of the individual unit.
• Inside TIA Portal, the Device information online view of the CPU shows the FS in a separate field, usually labelled Module / FS or visible in the diagnostic buffer. The firmware version is shown in an adjacent field labelled Firmware or Version. They are two independent numbers.

For a CPU 1215C with MLFB ending -0XB0, FS 12 is a normal production state that is fully compatible with TIA Portal V13 SP1 through V18 inclusive, provided the firmware selected in the project matches the firmware actually on the device. Encountering FS 12 is therefore not, on its own, an error condition.

3. S7-1200 Firmware Release History and TIA Portal Compatibility

The S7-1200 firmware releases are not forward-compatible. TIA Portal uses a specific project-side firmware image to compile user programs and to negotiate security, motion, and PROFINET features with the target CPU. A mismatch between the project's CPU firmware version and the running firmware on the device is the most common reason that an online operation fails.

To use firmware V4.6.x on a CPU 1215C, the engineering station must run TIA Portal V18 or higher. TIA V17 can compile a project for V4.5 only. TIA V16 can compile for V4.4 only, and so on. A V18 project opened in V17 will either be downgraded (with loss of newer functions) or refuse to load to a V4.6 CPU.

4. Symptom Catalogue: TIA Portal V18 Behaviour on a 6ES7215-1BG40-0XB0 with Firmware V4.6.1

The most common fault pattern is a brand-new or recently reflashed CPU 1215C returning download or online diagnostic errors against a TIA Portal V18 project. The following symptoms have been reproduced in the field and are the diagnostics a maintenance engineer should expect to see:

1. Online > Accessible nodes lists the CPU with the correct MAC address, but the device name is shown as UNKNOWN or S7-1200 station.
2. Online > Online and diagnostics opens, but the Module information tab displays firmware V4.6.1, while the project tree shows V4.1. A yellow triangle icon appears in the project tree next to the CPU.
3. Download to device finishes compilation but returns a dialog with the text "Firmware version of the online module (V4.6.1) does not match the configured version (V4.1). Do you want to proceed anyway?". Choosing No aborts the download.
4. Choosing Yes appears to complete the download, but the diagnostic buffer of the CPU records Event ID 0x01E4 / Event ID 0x138A entries referring to version mismatch, and the user program does not start cleanly.
5. Compare offline / online shows differences in the system data blocks that the editor cannot reconcile automatically.
6. The Online > Assign device name operation completes, but the device name does not survive a power cycle if the project is in a partially downloaded state.

5. Root Cause Analysis

Three independent causes can produce the symptoms above. Each must be eliminated in order before the next is investigated.

5.1 Project-side firmware not selected

The most frequent cause is a TIA project that was created on an earlier TIA Portal version, saved, and then opened in a newer TIA Portal. The CPU object in the project tree still references firmware V4.1 because that is what was originally selected. The newer TIA Portal will warn that the project uses a version that does not match the actual device, but it will not silently upgrade it. The Project tree > CPU > Properties > General > Catalog field still shows V4.1. The fix is to upgrade the project CPU firmware to match the device.

5.2 TIA Portal cannot push the firmware to the CPU

Some V4.x firmware images for the S7-1200 are larger than 4 MB. TIA Portal can normally push them over Ethernet through the PROFINET interface, but only if the project is in a consistent state and the SIMATIC Memory Card is in a writable state. If the previous download failed in the middle of a firmware transfer, the CPU may be in a recovery state and the only reliable way to recover is to write a fresh firmware image to a SIMATIC Memory Card externally and boot the CPU from that card.

5.3 Inconsistent "low-level component" versions in the project

Inside the project tree of TIA Portal, each module (CPU, signal module, communication module, I/O link) has a hidden module version attribute. These are the "low-level components" that must be fully compatible with the project firmware level. The TIA Portal Compatibility tool (menu Options > Support > Compatibility tool) enumerates these and offers a one-click path to update them. Until the version numbers in the project match the versions on the physical device, online operations will fail with one of the events above, even if the CPU firmware version is already correct.

6. Diagnostic Procedure (Online Access)

Before changing anything in the project, gather the device's actual state through the Online access path. This step is non-destructive.

1. Connect the engineering PC directly to PROFINET port X1 of the CPU 1215C with a Cat-5/Cat-6 patch cable. Do not go through a managed switch during diagnosis; the CPU's PROFINET port negotiates to 100 Mbit/s, full duplex, and a smart switch can mask link events.
2. Set the engineering PC Ethernet adapter to a static IPv4 address in the same subnet as the CPU's default IP. A S7-1200 with factory settings has no IP address, in which case the engineering PC should be in the 192.168.0.x / 24 subnet and the Online access > Network adapter > Accessible nodes function used to find the MAC and assign a temporary IP.
3. Open TIA Portal and open the project. In the project tree, expand Online access, expand the engineering PC's network adapter, and double-click Accessible nodes. The right pane populates with all reachable SIMATIC devices.
4. Right-click the CPU 1215C entry and select Online and diagnostics. The Diagnostics tab shows the firmware and FS in the Module information section.
5. Open the Diagnostic buffer tab. Record the most recent entries, in particular any with Event IDs 0x01E4, 0x138A, 0x138B, 0x43BE. These are the version-mismatch and firmware-transfer events.
6. Compare the recorded firmware with the firmware in the project (CPU > Properties > General > Catalog). If they differ, this is the root cause for download failures.

7. Resolution: Three Field-Proven Paths

The right path depends on what firmware is actually loaded on the CPU and what firmware is available in the user's TIA Portal installation.

7.1 Path A — Project firmware is older than the CPU

This is the situation when the project was created in TIA V13/V14/V15/V16/V17 and the CPU is running V4.6.1.

1. Install TIA Portal V18 (or a newer version that supports V4.6).
2. Open the project in V18. Right-click the project root and select Upgrade project.
3. Select the CPU 1215C in the project tree. Open Properties > General > Catalog. Change the firmware from V4.1 to V4.6.1. The Compatibility tool may show warnings for other modules; resolve each one in the same dialog.
4. Run Options > Support > Compatibility tool. The tool lists every module whose version is older than what V4.6.1 supports. Update each module's catalog reference to the recommended version. TIA Portal will refactor the project on confirmation.
5. Recompile. The lower-right status bar should show no errors and no warnings related to version mismatch.
6. Connect to the CPU as in section 6 and perform Download to device > Hardware and software (only if different). Confirm the prompt to overwrite the project online.
7. Power-cycle the CPU. The user program should start in RUN.

7.2 Path B — Project firmware is newer than the CPU (downgrade)

This is the situation when the user has TIA V18 but only has access to a CPU running V4.4 or V4.5. Downgrading the CPU's firmware is supported but requires a SIMATIC Memory Card.

1. Open TIA V18. In the project tree, right-click the CPU and select Online > Assign firmware version. The dialog lists the firmware images that the TIA V18 installation can deliver.
2. Select the version that matches the project's CPU reference. TIA Portal will offer to write that image to a SIMATIC Memory Card (the card must be empty, FAT-formatted, with a capacity supported by the CPU — 4, 12, 24, 256, or 2 GB).
3. Insert the card into the CPU. Power-cycle. The CPU detects the card and runs the firmware update from it. The status LEDs MAINT and LINK flash during the update; STOP is on solid. Do not remove power during this phase.
4. When the update is complete, the CPU returns to STOP. Remove the card. Re-read the firmware in the online view to confirm.
5. Re-attempt the project download.

7.3 Path C — Project firmware already matches the CPU but the download still fails

If both project and CPU show V4.6.1, the failure is at the level of an auxiliary component, usually a CM (communication module), SM (signal module), or a third-party PROFINET device. The fix is the Compatibility tool again, plus a check of the Device configuration > PROFINET interface > Topology for any device whose name has not been assigned.

1. Run Options > Support > Compatibility tool. Update every device whose version is not the latest TIA V18 reference.
2. Open Devices & networks. For every PROFINET device, right-click and Assign device name. Confirm the name was accepted by checking the device's BF LED — it must be off.
3. Compile the project, then download.

8. Working with a Used CPU 1215C

CPUs purchased on the secondary market (including from auction sites) can ship with one of three firmware states:

• Original factory firmware on the device label, typically V4.2 through V4.4 for the BG40 design.
• A later firmware flashed by a previous owner.
• A firmware that has been partially overwritten during a failed update — the CPU may then boot in a recovery mode and report an older firmware version than the one on the card.

If the label lists firmware V4.4 but the device only works with V4.1 selected in TIA, the most likely explanation is that the device's bootloader is intact and the original V4.4 firmware is in place, but the project-side module version of one or more auxiliary components in the project is set to a release that the V4.4 firmware does not recognize. Choosing V4.1 in the project hides those component versions behind the lowest-common-denominator set. The correct fix is to bring the project's auxiliary components to the V4.4 release set, not to keep the project at V4.1 indefinitely.

9. Verification Procedure

After applying any of the three resolution paths, run the following verification sequence. Each step has an expected state; if any step does not match, do not sign off on the commissioning.

1. Online identification. Open Online > Accessible nodes. The CPU's entry shows its assigned device name (not UNKNOWN), its IP address, and its firmware version.
2. Module information. Open Online and diagnostics > Module information. Firmware matches the project. FS is non-zero and matches the printed label. Hardware product version (ES) is non-zero.
3. Diagnostic buffer. The most recent event should be a clean Operating mode transition RUN or a download completion event. There should be no Event IDs in the 0x138x, 0x43Bx, or 0x01E4 ranges at the tail of the buffer.
4. User program start. Switch the CPU to RUN. The RUN LED is on solid. The ERROR LED is off.
5. Watch table. Add a watch table with one output bit (e.g. Q0.0). Force the bit, then verify with a hand-held voltmeter at the relay contact that the relay pulls in. This confirms the download did not just succeed at the data level but that the firmware actually controls the I/O.
6. Power-cycle test. Power the CPU down for at least 5 seconds, then up. The CPU comes back to RUN on its own if the project is configured for warm restart. If the project uses a SIMATIC Memory Card as the load memory, the user program reloads from the card automatically.

10. Field-Reference Tables

10.1 LED behaviour of the CPU 1215C during firmware update

10.2 Common Event IDs in the diagnostic buffer for version mismatch

10.3 FS reference for CPU 1215C BG40

11. Frequently Asked Questions