S7-1500 Online Backup Current Values, Retentive Memory

1. Overview

The Online Backup function in TIA Portal captures a snapshot of an S7-1500 (and S7-1200) CPU at a specific moment and stores it on the SIMATIC Memory Card. The snapshot is sufficient to restore a known-good configuration version of the controller — including its live, in-process data — without needing the original TIA project on hand. This makes online backup the cornerstone of any service workflow where engineers need to roll a machine back to a previous state, recover after a failed firmware update, or replicate a controller's runtime state onto a replacement unit.

Engineers frequently ask whether the current process values at the time of the backup become the start values on restore. The short answer is yes — and the long answer is what this document covers. The distinction between current values (loaded into the work memory at runtime) and start values (used to initialize the work memory on a STOP-to-RUN transition, cold restart, or restore) is the most common source of confusion in the field.

2. What the Online Backup Actually Stores

When TIA Portal executes Online > Backup from online device, the CPU writes a compressed archive to the memory card. According to the S7-1500 system documentation, the backup contains the data required to reconstruct the configuration version in its current operating state:

• Contents of the memory card — project data, recipes, user programs, and any data blocks that have been loaded to the card
• Retentive memory areas — data blocks flagged as retentive (DBs, instance DBs), retentive counters, retentive timers, and retentive bit memory (M) markers
• Retentive system data — IP address parameters, PROFINET device names, subnet masks, and router addresses that have been configured as retentive
• Current values of all data blocks at the moment the backup is taken (the runtime snapshot)

The backup operation does not require the original TIA Portal project to be present on the engineering station; the archive is self-describing. This is the reason it is so valuable for remote service calls where the engineer never had the source project.

3. Current Values vs. Start Values: The Critical Distinction

The terms current value and start value have precise meanings in STEP 7 / TIA Portal and are not interchangeable.

When a backup is taken, the CPU serializes the contents of work memory, including the live, runtime-modified values. On restore, those live values become the new start values of the affected blocks. In other words, the captured snapshot is the authoritative initialization state until the user loads fresh start values from a TIA project.

4. Retentive vs. Non-Retentive Memory Areas

Retention is configured per-tag in data blocks and via global settings for M, C (counters), and T (timers). The retention settings are stored as part of the project and are part of the online backup.

A common field mistake is assuming all DB values are retained. Only the explicitly ticked tags survive a power cycle, and only those ticked tags are recoverable from an online backup of a CPU that was in RUN at the time of capture.

5. Creating an Online Backup in TIA Portal — Step-by-Step

Prerequisites:

• Online connection to the target CPU (PROFINET, PROFIBUS, Ethernet, or TeleService) — see S7-1500 System Manual, section "Online functions"
• Memory card installed with sufficient free space (S7-1500: ≥ 2 MB recommended for a typical project)
• PG/PC with the same or newer TIA Portal version that compiled the original project (newer TIA Portal can read older archives)
• User rights in the project: at least "Read" online access

1. In the project tree, expand Online > Accessible devices and confirm you can see the target CPU.
2. Select the CPU and choose Online > Backup from online device (keyboard shortcut: Ctrl+Alt+B on most TIA Portal versions).
3. Confirm the memory card path. The default is the internal SIMATIC Memory Card; on S7-1500 with a display, you can also select external storage via the display's Service menu.
4. Choose whether to back up the current user program only or to include all online data (recommended for service recoveries — include all data).
5. Click Backup. Progress is shown in the Inspector window. Typical duration: 5–60 seconds for a small project; multi-MB projects may take several minutes.
6. When complete, TIA Portal prompts for the archive file name and path. Save it to the project folder for traceability.

For unattended / headless deployments (S7-1500 CPU without display, or S7-1200), this TIA Portal path is the only built-in option. The resulting .s7pbkp file is portable and can be restored on a different CPU of the same article number.

6. Creating a Backup via the S7-1500 Display (No Engineering Station Required)

S7-1500 CPUs with a removable display panel (e.g., 6ES7531-7LH00-0AB0) can perform a backup directly from the device, which is critical when no PG is on site.

1. Navigate Settings > Backup > Create backup on the display.
2. Select the backup type: Complete backup (recommended) or User-defined (advanced — choose specific DBs).
3. Choose the destination: internal SIMATIC Memory Card or an externally inserted SD card in the display (where supported).
4. Confirm. The display shows a progress bar and writes a .s7pbkp file that can later be read by TIA Portal.

This path is the field-recommended approach for S7-1500 service calls where the customer cannot host a VPN session for the engineer. The backup file can be emailed and restored onto a different CPU of the same order number without needing the original TIA project.

7. Restoring from an Online Backup

1. Establish online connectivity to the target CPU.
2. Choose Online > Restore from online backup.
3. Browse to the .s7pbkp file.
4. TIA Portal validates the article number (MLFB), firmware version compatibility, and project structure. Mismatches are flagged — see Siemens KB 81318674: "Compatibility of TIA Portal versions with the S7-1500 CPU firmware" for the cross-version matrix.
5. Confirm the restore. The CPU goes to STOP, the load memory is overwritten, and on the next RUN transition the captured start values are applied.
6. Verify the result by going online and monitoring the affected DBs — the values should match what was on the source CPU at backup time.

8. What Is NOT Included in the Backup (Documented Limitations)

The backup is intentionally an operational snapshot, not a complete forensic image. The following are not captured:

• Diagnostics buffer entries — these are runtime event logs and are not part of the configuration version. They are not preserved across backup/restore. If post-incident analysis is required, export the diagnostics buffer before the backup using Online > Diagnostics > Diagnostics buffer in TIA Portal.
• Current time of day — for S7-1500 CPUs, the TOD clock is not backed up. On restore, the CPU will start with whatever time is provided by NTP, a paired HMI, or a manual set. Configure NTP synchronization prior to RUN, or accept the time skew.
• Non-retentive DB tags and M markers — these are reset to their start values, not to the live snapshot, because the live snapshot is overwritten during a STOP transition.
• Process image I/Q values — physical I/O is re-read on the next OB1 cycle, not restored.
• Local stack / TEMP variables — by definition, these are runtime-only.
• Firmware of the CPU — the backup assumes a compatible firmware is already flashed. To upgrade or downgrade firmware, use TIA Portal's Online > Firmware update function separately.

9. Field-Proven Update Workflow

Combining a TIA project update with a snapshot is the safest pattern for remote service:

1. Before the engineer arrives on site: Customer uses the S7-1500 display (or a local PG) to perform a complete backup of the running machine. The .s7pbkp is sent to the engineer.
2. Engineer prepares the update offline: Open the customer's TIA project, apply the program changes, compile.
3. Engineer arrives (or connects via VPN): Online > Compare offline/online to confirm the running version matches the starting TIA project.
4. Apply the update: Download the modified blocks. Optionally, before download, capture the live runtime values (recipe parameters, production counters) and paste them into the new DB as new start values if the schema changed.
5. Verify and back up again: After commissioning, take a fresh backup to capture the new running state.

This pattern — backup before, update, backup after — is the de facto industry standard for S7-1500 service and mirrors the field recommendation: "Always ask the customer to provide a PLC backup."

10. Verification and Acceptance Test

After any backup or restore, run a structured acceptance test before handing the line back to production:

1. Confirm CPU is in RUN, no SF/BF LEDs lit (see S7-1500 System Manual — LED diagnostics).
2. Open the diagnostics buffer in TIA Portal and verify no new errors since the restore (note: pre-existing buffer entries are gone — that is expected behavior).
3. Monitor each retentive DB and confirm values match the pre-backup snapshot.
4. For each non-retentive DB, confirm values are the project-defined start values, not the captured snapshot.
5. Trigger a manual STOP→RUN transition and observe whether any data changes unexpectedly — a clean transition indicates the start values are coherent.
6. Verify the time-of-day clock is correct (NTP sync, HMI sync, or manual set).
7. Run the machine through a complete production cycle to confirm I/O and motion behavior.

11. Comparison: S7-1200 vs S7-1500 Online Backup

Functionally, the S7-1200 backup behavior is a subset of the S7-1500. The S7-1500's primary advantage for service is the display panel, which allows the backup to be initiated by the customer without installing TIA Portal locally.

12. Troubleshooting Matrix

FAQ