S7-1200 1212C Firmware V2.2 Update: Fix Wrong MMC and EXE Errors

Overview

The SIMATIC S7-1200 CPU 6ES7 212-1HD30-0XB0 (1212C DC/DC/Relay) ships from the factory with firmware V1.0 and is field-upgradeable to V2.2.x via the front-panel SIMATIC Memory Card (SMC) slot. The update procedure is documented in the Siemens Industry Online Support portal and uses a self-extracting Windows executable (.EXE) whose output is written to the \SIMATIC\S7_1200\FWUPDATE directory on the SMC. The PLC bootloader reads this directory at the next power-up and applies the firmware, then signals completion with a specific LED pattern.

When the procedure terminates early — for example at V2.1 instead of V2.2 — the root cause is almost always one of three things:

1. The memory card in use is not a SIMATIC SMC. The 6AV6671-1CB00-0AX2 is an MMC designed for S7-300 / ET 200S, not for the S7-1200.
2. The firmware executable extracted to the card does not match the exact MLFB (order number) of the target CPU, including the I/O variant suffix (DC/DC/DC vs. DC/DC/Relay vs. AC/DC/Relay).
3. The card contains multiple firmware .UP files in the FWUPDATE directory. The bootloader selects the first valid match and stops, leaving the remainder unprocessed.

This reference walks through identification of the correct SMC, the correct firmware file name pattern, the LED-based status decoding, the recovery procedure when V2.1 is reported as the active version, and a verification matrix that confirms a clean V2.2 install.

Affected Hardware and Required Components

Firmware File Naming Convention

The Siemens .EXE firmware updater for the S7-1200 always uses the order number (MLFB) of the target module in the file name. The string between the underscores breaks down as follows:

212-1HD30-0XB0_V220.EXE
│   │       │    │
│   │       │    └── V2.2.0 firmware build
│   │       └─────── Hardware variant suffix (-0XB0 = DC/DC/Relay, -0XB1 = DC/DC/DC)
│   └─────────────── Product family / I/O group
└─────────────────── Module family code (2 = CPU 12xx)

Common 1212C variants and their matching update files:

Do not assume that two CPUs with the same I/O count are interchangeable. The HD30 vs. HD40 difference, for example, reflects a hardware revision that requires its own firmware. Loading the wrong file appears to the user as a successful update (LEDs cycle, MAINT stops flashing), but the firmware level reported in TIA Portal is unchanged, or worse, the PLC enters a recurring reboot loop.

Root Cause Analysis: Why the Update Stops at V2.1

Three root causes produce the symptom "update appears to run, but firmware level remains at V2.1 (or any pre-V2.2 level)":

Root Cause 1 — Wrong SMC Catalog Number

The 6AV6 671-1CB00-0AX2 is a 4 MB MultiMediaCard intended for S7-300 CPUs. The S7-1200 SMC slot is electrically and mechanically compatible with the SD-card-form-factor SMCs in the 6ES7 954-8L family, but the bootloader requires a SIMATIC SMC with the correct filesystem structure. When a non-SIMATIC card or an S7-300 MMC is inserted, the PLC's update routine either:

• Reads the card, finds no valid FWUPDATE directory, leaves the firmware untouched, but the operator may misread the LED pattern as a successful update; or
• Partially processes the file and stops at the next non-matching point, leaving the previous firmware (e.g., V2.1) intact.

Root Cause 2 — Mismatched EXE in the Update Directory

If the extracted FWUPDATE folder contains a file for a different MLFB — e.g., 1214 firmware (214-1BD30-0XB0) copied to a 1212C, or DC/DC/DC firmware (212-1BD30-0XB0) on a DC/DC/Relay CPU (212-1HD30-0XB0) — the bootloader validates the order number against the CPU's hardware ID. On mismatch, the bootloader reports a "firmware not for this module" condition. The PLC remains in its previous state (often V2.1 after a prior good update from V2.0).

Root Cause 3 — Multiple Firmware Files in FWUPDATE

If two or more valid .UP files are present (for example, a V2.0 leftover plus a V2.2 fresh extract), the bootloader processes the first valid match alphabetically and stops. It does not iterate to the higher version automatically. The user sees what looks like a successful update, but the level reported is whichever file was processed first.

Pre-Update Verification

Before inserting the card, perform these checks. Any failure here saves an entire update cycle.

1. Confirm CPU MLFB. Read the label on the front of the CPU. Confirm the exact string, including every character of the suffix. Photograph the label if needed. The PLC's own diagnostic buffer in TIA Portal also reports the order number under Online & Diagnostics > Diagnostics > Module Information > Identification.
2. Inspect the SMC. Read the part number laser-etched on the card. Acceptable SMCs for S7-1200 firmware update begin with 6ES7 954-8L. Anything in the 6AV6 671-1 family is not an SMC.
3. Verify file integrity on the PC. Right-click 212-1HD30-0XB0_V220.EXE > Properties > Digital Signatures. The signer should be "Siemens AG". If the file was repackaged or truncated, the bootloader will reject it at the CRC check and the PLC will not change state.
4. Format the SMC. Use only the Siemens SIMATIC Automation Tool, the S7-1200 Program Card utility in TIA Portal, or a clean SD-formatter from the SD Association. Windows quick-format is acceptable provided the filesystem is FAT or FAT32 and a single primary partition is present. A card with an MBR from another tool may not be readable by the PLC.
5. Extract to a known path. Run the .EXE and extract directly to the root of the SMC. The resulting tree should be:\pre>\\SMC\SIMATIC\S7_1200\FWUPDATE\S7_1200.WUP \\SMC\SIMATIC\S7_1200\FWUPDATE\ORDER.TXT (optional)
6. Confirm a single firmware target. The FWUPDATE directory must contain exactly one .UP or .WUP payload. Any second file must be removed.

Step-by-Step Firmware Update Procedure

1. Bring the PLC to STOP. Either turn the mode switch to STOP, or stop the CPU from TIA Portal. Wait for the RUN LED to be off and the STOP LED to be solid yellow.
2. Insert the SMC. With power applied, push the card into the slot on the underside of the CPU module until it clicks. Do not use excessive force — the card is keyed.
3. Power-cycle the PLC. Remove and re-apply the 24 V supply. The PLC will boot into the firmware-update routine because it detects a valid FWUPDATE directory on the SMC.
4. Observe the LED sequence. The expected pattern during a V2.2 update from V2.x takes 2 to 5 minutes. See the LED state diagram below.
5. Wait for the MAINT LED to stop flashing and the RUN LED to be solid yellow. The PLC is in the post-update state but not yet running the user program.
6. Remove the SMC. The card is no longer needed and the PLC will not boot normally with the FWUPDATE directory still present.
7. Power-cycle the PLC. The PLC should boot into RUN (or remain in STOP per the mode switch position) with the new firmware active.
8. Verify in TIA Portal. Go online, right-click the CPU, and read the firmware version under Online & Diagnostics > Diagnostics > Module Information. Confirm it shows 2.2.x, not 2.1.x.

LED Status Decoding During the Update

Troubleshooting Matrix

Verification Steps After a Successful Update

1. In TIA Portal, go online with the CPU.
2. Open Online & Diagnostics &em> Diagnostics > Module Information.
3. Confirm the firmware version is reported as 2.2.x.
4. Open the diagnostic buffer and look for the entry Firmware update successful with a corresponding timestamp.
5. Cycle power to the PLC and confirm it boots into RUN (assuming a program is loaded) and that the user program executes without an I/O error storm.
6. Re-download the project to confirm tool-to-PLC firmware compatibility — STEP 7 V11 SP2 supports V2.2 projects; older versions will reject the connection.

Recovery Procedure When the Update Has Been Performed with the Wrong File

If the firmware has been partially updated and the PLC is stuck at V2.1 or the bootloader is rejecting the file mid-write, perform the following recovery:

1. Power down the PLC.
2. Remove the SMC.
3. On a Windows PC, use a card reader to wipe the SMC (full format, FAT32, default allocation size).
4. Re-download 212-1HD30-0XB0_V220.EXE from the Siemens Industry Online Support portal. Verify the file size matches the published value on the download page.
5. Run the EXE and extract to the SMC root.
6. Confirm only one .UP/.WUP file exists in \SIMATIC\S7_1200\FWUPDATE.
7. Insert the SMC into the PLC, power up, and observe the LED sequence described above.
8. If the PLC still does not advance, perform a factory reset by writing an empty program card (SMC with a fresh S7_JOB\S7_1200 SIMATIC structure) and re-attempting the firmware update on a different SMC of the same catalog family.

Process Flow: Diagnostic Decision Tree

Reference: SIMATIC SMC Family for S7-1200

Safety and Operational Notes

• Do not remove the SMC while the MAINT LED is flashing during the write phase. Interrupting the write can leave the PLC in a state that requires a factory reset via an empty program card.
• Do not cycle power during the firmware update. The PLC's internal flash is being rewritten, and an interruption can cause an irrecoverable boot failure.
• Update the project to a STEP 7 version that supports the target firmware (V2.2 requires STEP 7 V11 SP2 Update 2 / V12 SP1 / V13 or later). Older TIA Portal versions will refuse to connect to a V2.2 CPU.
• If the CPU is part of a safety-related application (fail-safe variant -0XB0 F), confirm the F-firmware version is consistent. S7-1200F updates use a different SMC procedure and a different EXE name.
• After the update, perform a complete backup of the project to the SMC using TIA Portal's Online > Backup from online device to a freshly formatted card, to provide a rollback point.

FAQ