Deleting MMC Load Memory in TIA Portal V12: S7-300/1500 Methods

1. Overview: The MMC/MC Memory Card Erasure Problem in TIA Portal V12

Engineers migrating from SIMATIC Manager (Step 7 V5.5) to TIA Portal V12 frequently encounter a hard limitation: there is no built-in, point-and-click MMC load-memory wipe command inside the TIA Portal V12 project tree comparable to the legacy "Delete User Program / Reset to Delivery State" sequence on the S7-300 CPU front panel or to "PLC > Erase RAM" in NetPro. The TIA Portal V12 Online & Diagnostics tree exposes Format Memory Card, Assign Memory Card as Program Card, and Assign Memory Card as Firmware Card for S7-1500 and S7-1200 SIMATIC Memory Cards (SIMATIC MC) only. For S7-300 Micro Memory Cards (MMC, 3.3 V, 7-pin or 14-pin slot), TIA Portal V12 deliberately does not offer a formatting path because the underlying S7-300 CPU firmware does not implement the SD/MMC controller host commands required for block-erase over the backplane bus. Erasing an S7-300 MMC therefore requires either an external Siemens USB prommer (S7-PROM / Field PG prommer) or the MMC slot built into a Siemens Power PG (e.g., 6ES7710-0....).

This article consolidates every viable erasure procedure for TIA Portal V12 and its supported controllers (CPU 31x, CPU 121x, CPU 151x) and documents the firmware-version boundaries where each method becomes available. The content is written for commissioning engineers who must either wipe a corrupted card before re-download, return a project to a known-clean state, or recover a bricked CPU through firmware re-flash from a freshly erased card.

2. Hardware Distinction: S7-300 MMC vs S7-1500 MC vs S7-1200 MC

The naming alone trips up a lot of field engineers: Siemens rebranded the same physical media between platform generations, and the controller-side tooling reflects that. The table below summarizes the engineering-relevant differences.

3. Why TIA Portal V12 Cannot Delete S7-300 MMC Contents

SIMATIC S7-300 CPUs (CPU 312, 314, 315-2 DP, 317-2, 319-3 PN/DP, and their F variants) implement the load-memory interface through a dedicated MMC controller ASIC. The CPU operating system exposes the card to STEP 7 / TIA Portal as a flat block store, not as a filesystem. Commands that TIA Portal sends to the online PLC over Industrial Ethernet or MPI/PROFIBUS are limited to:

• Download block (OB/FB/FC/DB/SDB) into load memory
• Compress load memory (MRES-equivalent via online command)
• Delete single block from load memory (right-click on Online > Online blocks)

There is no SCP / block-erase primitive defined in the S7-300 backplane protocol for "delete all blocks" or "low-level format MMC". The legacy "MRES" button on the CPU front panel performs a logical reset of work memory but does not erase the MMC; it only invalidates the boot pointer. The Step 7 V5.5 SIMATIC Manager > PLC > Erase RAM dialog worked because it issued the obsolete, MMC-aware erase SFC sequence against the CPU firmware — a path that TIA Portal V12 dropped when Siemens moved the S7-300 backplane driver out of the unified TIA framework.

Engineers therefore hit a wall: deleting individual blocks from the TIA Portal Online tree removes the runtime copies but leaves the MMC byte image untouched. The free-space display in the online diagnostics may still show 0% free even after every visible block is removed, because the compressed-log image is not reclaimed.

4. Solution 1: Formatting S7-1500 MC via TIA Portal Online & Diagnostics

For SIMATIC S7-1500 CPUs (CPU 1511-1 PN through CPU 1518-4 PN/DP, plus the ET 200SP CPU 1510/1512/1515/1516) running firmware V1.0 or later, TIA Portal V12 (build 12.0.0.0 or higher, SP1 recommended) provides a native, low-level format of the SIMATIC MC.

Prerequisites

• TIA Portal V12 SP1 or higher installed (V12.0.0.0 misses some CPU FW ≥ 2.x card formats)
• S7-1500 CPU running firmware V1.0+ (V1.5+ recommended for reliability)
• Ethernet TCP/IP path between the engineering PG and the PLC (PROFINET interface X1 or X2)
• Configured device in the project (or use "Accessible nodes" without project)
• PG/PC interface set to the correct NIC in Control Panel > Set PG/PC Interface

Step-by-Step Procedure

1. Power on the CPU and confirm the RUN/STOP/MRES switch is in STOP.
2. Insert the SIMATIC MC into the slot on the CPU. The RUN LED will blink briefly during card detection.
3. In TIA Portal V12 project tree, right-click the CPU 151x device and choose Online & Diagnostics.
4. From the diagnostics tree, expand Functions.
5. Select Format memory card. The dialog shows the current card model (e.g., 6ES7 954-8LE03-0AA0, 12 MB) and the active file system.
6. Confirm the dialog. TIA Portal prompts: "All data on the memory card will be deleted. The CPU will be reset to factory settings. Do you want to continue?" Click Yes.
7. The progress bar runs for 5 to 60 seconds depending on card size. The CPU transitions to STOP with memory reset; the MAINT LED may blink if configured.
8. When the status bar shows Formatting completed successfully, close the dialog.
9. Re-download your project to the PLC via Online > Download to device (Ctrl+L).

5. Solution 2: Formatting S7-1200 MC via TIA Portal Online & Diagnostics

The S7-1200 platform (CPU 1211C, 1212C, 1214C, 1215C, 1217C, 1212C DC/DC/DC, all DC/DC/Rly and AC/DC/Rly variants) supports memory card formatting from firmware V4.0 onwards, which corresponds to TIA Portal V12 SP1 project compatibility. The dialog is identical to the S7-1500 path but appears under the CPU 121x online tree.

1. Switch the CPU 121x mode selector to STOP.
2. Insert the SIMATIC MC (4 MB, 12 MB, 24 MB catalog numbers) into the slot on the front of the CPU.
3. In TIA Portal V12, navigate to Project tree > [CPU 121x] > Online & Diagnostics.
4. Expand Functions → Format memory card.
5. Click Format and confirm the warning.
6. Wait for the success message. The card is now a clean SIMATIC MC, ready for project download.

Alternative: Assigning the Card as Program Card or Firmware Card

TIA Portal V12 exposes two additional Functions entries on the S7-1200 / S7-1500 online tree:

• Assign memory card as Program Card — binds the card to the CPU as load-memory extension. After formatting, the card becomes the exclusive load-memory store and removing it leaves the CPU unable to start without a card.
• Assign memory card as Firmware Card — writes the selected firmware update file (e.g., S7_1200_CPU1215C_V4_2_3.upd) onto the card. On next CPU power-up with the card inserted, the CPU performs a forced firmware update.

6. Solution 3: External USB Prommer for S7-300 MMC

For S7-300 MMC erasure where TIA Portal V12 cannot help, the proven path is a Siemens USB prommer. Two product options exist:

Procedure with S7-PROM USB (6ES7 792-0AA00-0XA0)

1. Insert the MMC into the prommer slot. The orange LED indicates power; green indicates ready.
2. Launch SIMATIC Manager V5.5 SP4+ on the PG (the prommer ships with the legacy EPROM programming tool S7-EPROM Programmer, located in Start > SIMATIC > STEP 7 > S7-EPROM Programmer).
3. In the EPROM programmer UI, click File > Open MMC and select the inserted card.
4. Click File > Delete MMC. The tool performs a full block-erase of the MMC and writes a fresh Siemens master boot record (MBR).
5. Verify the card by reading the block table; expected count of user blocks = 0.
6. Eject the card and insert it back into the S7-300 CPU. Download the new project via TIA Portal V12 or SIMATIC Manager.

Procedure with Field PG Integrated Prommer

1. Power on the Field PG (e.g., SIMATIC Field PG M5 6ES7 715-1...-...).
2. Insert the MMC into the slot behind the access flap on the front of the PG.
3. Open SIMATIC Manager > Options > S7 Memory Card.
4. Select the inserted card from the dropdown.
5. Click Erase then Format. Confirm both operations.
6. Verify with Display that the free-space field reports the full card capacity.

7. Solution 4: Programmatic File Deletion on S7-1200/1500 with FileDelete

For ongoing runtime housekeeping — e.g., deleting archived CSV files on the SIMATIC MC without removing the card — the S7-1200/1500 instruction set provides the FileDelete extended instruction, documented in the SIMATIC S7-1200 manual collection at TIA Portal — FileDelete: Delete file on the memory card.

Interface Definition

Sample Code (SCL, TIA Portal V12)

// FB "DeleteCsvArchive" — removes a single CSV on the SIMATIC MC
#FileDelete_0(REQ := #bTrigger,
              NAME := '\LOG\' + #sFileName);

IF #FileDelete_0.DONE THEN
    #iState := 20;          // proceed to next file
    #bTrigger := FALSE;
ELSIF #FileDelete_0.ERROR THEN
    CASE #FileDelete_0.STATUS OF
        16#0001: #sLog := 'File is currently open, close first';
        16#0002: #sLog := 'File not found';
        16#0003: #sLog := 'No authorization';
        16#7000: #sLog := 'No operation in progress';
        16#8090: #sLog := 'Name parameter contains invalid characters';
        16#8091: #sLog := 'Wildcards not supported in Name';
        16#80A2: #sLog := 'File system error';
        16#80B0: #sLog := 'Card write-protected';
        16#80B4: #sLog := 'Card removed during operation';
        ELSE       #sLog := 'Unknown FileDelete error';
    END_CASE;
END_IF;

Important Constraints from the Siemens Documentation

• The file must be closed before deletion (close any open FileOpen handle first).
• Wildcards (*, ?) are not supported in the Name parameter despite legacy forum posts claiming otherwise. To delete multiple files, iterate the FileDelete call from a generated list (e.g., via FileReadDir).
• The instruction requires a SIMATIC MC inserted into the CPU; without a card, STATUS returns 16#80B4.
• The instruction is available in TIA Portal V12 SP1 and later; V12.0.0.0 lacks the file-handling palette.

8. Firmware Recovery: Re-flashing the CPU via TIA Portal Online & Diagnostics

If an MMC is corrupted to the point the CPU will not boot, TIA Portal V12 provides a firmware-loader path that can rewrite the MMC and the CPU firmware simultaneously. This is the same dialog exposed by Online & Diagnostics > Functions > Firmware update.

1. From the Siemens support site support.industry.siemens.com, download the firmware update file for the target CPU. For example: CPU_1215C_V4_2_3.upd for S7-1200 CPU 1215C firmware V4.2.3, or CPU_1516_PN_V2_6_0.upd for the S7-1500 CPU 1516-3 PN/DP V2.6.0.
2. Power the CPU to STOP. Insert a SIMATIC MC (formatted via the procedure in Section 4 or 5).
3. In TIA Portal V12, open Online & Diagnostics > Functions > Firmware update.
4. Browse to the downloaded .upd file. TIA Portal validates the file against the CPU type and current firmware.
5. Click Run update. The CPU may go through a power-cycle internally; do not interrupt.
6. Once the dialog reports success, power-cycle the CPU manually and re-download the project.

9. Method Comparison Matrix

10. Verification Procedure After Memory Card Wipe

1. Insert the freshly wiped card into the CPU. Power on the PLC.
2. Watch the STATUS LEDs:
   • S7-300: BF off, SF off, RUN green — clean state.
   • S7-1200: STOP yellow or RUN green depending on project presence.
   • S7-1500: MAINT blinks briefly then OFF, RUN green if project downloaded, STOP yellow if not.
3. In TIA Portal V12, connect Online > Go Online. Right-click the CPU and choose Online & Diagnostics > Diagnostics > Diagnostics buffer. The most recent entry should reference card format / empty project.
4. Verify in Online & Diagnostics > Memory the reported free-space equals the full card capacity (e.g., 12.0 MB on a 12 MB SIMATIC MC, 7.8 MB on an 8 MB MMC).
5. Perform a full project download: Online > Download to device > Hardware and software (only if different).
6. After successful download, switch the CPU to RUN and observe the diagnostic buffer for any residual SFC/SFB errors.

11. Common Errors and Field-Proven Workarounds

12. FAQ