Siemens S7-300/400 Report System Error: Configuration Guide

Overview

Report System Error (RSE) is the Siemens diagnostic generator that ships with STEP 7 V5.x and the equivalent System Diagnostics with Report System Errors tool inside TIA Portal. The wizard reads the hardware configuration (HW Config) of an S7-300 / S7-400 station together with all its DP / PN / AS-i slaves, then automatically writes the diagnostic function blocks, the instance DB, the relevant error OBs, the standard message texts, and the WinCC / WinCC flexible alarm log connection. The end result is a uniform, channel-accurate diagnostic display on the HMI without writing a single line of application code.

RSE is the recommended Siemens replacement for hand-coded SFB 52 / SFB 54 / SFB 81 diagnostic reads in STEP 7. It is the same diagnostic backbone used by ET 200S, ET 200M, ET 200pro, DP/AS-i LINK Advanced, and the majority of Siemens cataloged slave diagnostics.

Prerequisites

• STEP 7 V5.5 SP2 or later (or STEP 7 V5.6) for classic projects, or TIA Portal V16+ for the modern equivalent.
• S7-300 CPU 31x or S7-400 CPU 41x with firmware that supports diagnostic interrupts (essentially all standard CPUs except very early 312 IFM / 314 IFM).
• S7 Program: at least one OB1, OB100 (restart), and the diagnostic OBs the wizard will write (OB 80, 82, 83, 85, 86, 121, 122).
• HW Config fully compiled with all slaves parameterized and known to the catalog.
• For HMI display: WinCC V7.x, WinCC flexible 2008 SP3+, or a Comfort/Classic panel configured against the S7 station.
• Siemens support ID for RSE with DP/AS-i LINK Advanced: How do you implement the 'Report System Error' function with DP/AS-i LINK Advanced?

How RSE Works Internally

When the wizard is invoked, STEP 7 performs the following actions:

1. Walks the HW Config tree, extracting the slot number, module order number, channel count, and diagnostic capability of every module.
2. Generates FB 126 (RSE_FB) – the cyclic diagnostic evaluator.
3. Generates DB 126 – the instance DB that holds the symbol list, the diagnostic status, and the message buffer.
4. Generates or updates the diagnostic OBs (OB 82, OB 83, OB 86, and optionally OB 121 / OB 122).
5. Generates the standard message texts in German, English, French, Italian, Spanish, and Chinese (depending on installed language pack) – each message is identified by its EV_ID (event ID).
6. Creates the WinCC connection "S7 Diagnosis" or "RSE" with the alarm-logging tag mapping.
7. Generates an entry for the DP/AS-i LINK Advanced (firmware V2.x and higher) where applicable.

At runtime, OB 82 fires on every diagnostic interrupt from a module, OB 83 on hot-swap insert/remove, OB 86 on rack/DP-slave failure, and OB 122 on access errors. RSE FB 126 then formats these events into the WinCC message structure and updates the message buffer in DB 126.

Classic STEP 7 Configuration (SIMATIC Manager)

Step 1: Open HW Config

Open the S7 project, select the S7 station, then double-click Hardware. Wait until the hardware tree is fully expanded and any catalog sync (HSP update) is complete. RSE depends on a clean compile: a yellow warning in HW Config means the wizard cannot resolve a slot.

Step 2: Launch the Wizard

Right-click the station header (rail 0) and choose Report System Error. In STEP 7 V5.5 the wizard is found at Station → Report System Error; in V5.6 the menu item is identical.

Step 3: Configure the Wizard Options

Step 4: Compile and Download

Press Generate. The wizard produces the blocks, then Save and Compile the HW Config. Download HW Config + the S7 program (FB 126, DB 126, OBs) to the PLC and perform a cold restart (OB 100) so DB 126 is initialized.

Step 5: Activate Message Texts

If WinCC is in the same project, open WinCC Explorer, then Alarm Logging → Tools → Import. Import the .txt files generated under S7 Program → Sources → RSE. Each message text becomes an alarm row with the EV_ID as the message number.

TIA Portal: System Diagnostics with Report System Errors

In TIA Portal the wizard is invoked from the device view: right-click the CPU and choose Properties → System Diagnostics → Report System Errors. The configuration is otherwise equivalent to the classic wizard but is integrated into the device configuration rather than HW Config.

The official entry point for the modern TIA Portal workflow is the documentation page Introduction to system diagnostics with Report System Errors (S7-300 / S7-400).

Diagnostic FBs and Error OBs

RSE generates or updates the following building blocks. The table below lists the standard slot numbers; user programs must not overwrite these unless the wizard is re-run.

Calling FB 126 Manually

For most stations the auto-call chain from OB 82/83/86 is sufficient. If you need cyclic refreshes (e.g., to detect intermittent channel faults that do not raise an interrupt), call FB 126 once per OB1 cycle:

CALL "RSE_FB" , "RSE_DB"
  MODE     := 1    // 0 = cyclic, 1 = single
  RACK_NO  := 0    // local rack, or DP slave PROFIBUS address
  SLOT_NO  := 4    // module slot
  RET_VAL  := MW100

Set MODE = 1 for one-shot reads on demand; MODE = 0 runs the full sweep on every call (heavier on CPU but covers diagnostic data the OB chain does not surface).

Message Text Structure

Every diagnostic event becomes a WinCC alarm. The message text follows a fixed template:

@1C%t@ System: @2C%t@ Event: @3C%t@ Slot: @4C%t@ Channel: @5C%t@ @6C%t@
Status:  @7C%t@
Diagnostic: @8C%t@

The @nC%t@ placeholders are filled by RSE with:

1. System identifier (CPU type / station name)
2. Event class (Fault, Maintenance, Information)
3. Event ID (mapped to the cataloged diagnostic of the module)
4. Slot number and module order number
5. Channel number (0-based)
6. Module channel description from the catalog
7. Status word (qualifier + maintenance + fault bits)
8. Free-form diagnostic text from the manufacturer

The EV_ID numbering for S7-300/400 starts at 16#0000_0001 for the CPU itself and increments per slot. ET 200S modules use a 1000-step per DP-slave base; ET 200M modules use a 100-step per slot base. The HMI tag EV_ID on WinCC side is a DWORD; pass it through the standard WinCC alarm structure.

WinCC and WinCC flexible Integration

WinCC V7.x

1. Open WinCC Explorer of the integrated project.
2. Right-click Alarm Logging → Open.
3. Select Tools → Import → STEP 7 Message Texts.
4. Browse to S7 Program → Sources → RSE → *Language*.txt.
5. Confirm; the EV_IDs become WinCC message numbers, the texts become the alarm lines.
6. Wire the WinCC tags RSE_Input / RSE_Output (raw + status) to the corresponding WinCC alarms.
7. Add the standard WinCC picture "SYSTEM_DIAG" to the HMI runtime – it displays the message buffer live.

WinCC flexible

WinCC flexible does not import the STEP 7 message texts automatically; the message texts must be regenerated with the panel's catalog (Tools → Report System Error for Panels). The result is the same EV_ID ↔ text mapping. On the panel, insert the "System Diagnostics" view from the library; it shows current and historical events.

Comfort Panels and WinCC Unified

Under TIA Portal the message texts are part of the HMI configuration; the panel proxy receives them through the HMI compilation. No manual import step is required.

DP/AS-i LINK Advanced Variant

When the project includes a DP/AS-i LINK Advanced gateway (e.g., 6GK1411-5AB00 or 6GK1411-5AB10), the RSE wizard extends the diagnostic coverage to the AS-i slaves hanging off the gateway. The wizard generates additional symbolic entries for every AS-i slave address discovered during HW Config, including power supply faults, slave presence, and analog out-of-range events.

Implementation steps are documented by Siemens support under the article How do you implement the 'Report System Error' function with DP/AS-i LINK Advanced?. Key points:

• Firmware of the gateway must be V2.0 or later.
• Diagnostic capability per AS-i slave must be enabled in the AS-i configuration tool (AcConNet or STEP 7 HW Config).
• RSE generates the additional symbol names prefixed with ASi_ (e.g., ASi_Slave_3B).
• The DP/AS-i LINK Advanced itself appears as a standard DP slave and consumes one DP diagnostic slot in the EV_ID range.

Commissioning and Verification

1. Download all blocks and the HW Config to the PLC; run OB 100 (warm restart).
2. Open STEP 7 → PLC → Diagnostic Buffer; verify the last entry reads "RSE initialized" (catalog text).
3. In WinCC / WinCC flexible runtime, open the System Diagnostics view.
4. Pull a single channel on a digital ET 200S module. Expected: a "Channel fault" alarm with the correct slot, channel, and order number.
5. Disconnect a DP slave PROFIBUS connector. Expected: an OB 86 alarm "Rack failure DP slave X".
6. Reconnect. Expected: the alarm clears automatically (acknowledgement model "without acknowledgement" for transient faults).
7. Force a programming error (insert L DW 1000 on an undefined DB). Expected: OB 121 fires, the diagnostic view shows "Programming error".
8. Remove an ET 200S module while in RUN. Expected: OB 83 fires for both remove and re-insert events.

Verification commands in STEP 7 V5.x:

PLC → Diagnostic/Setting → Module Information
  -- Tab "Diagnostic Buffer" shows OB 82/83/86 entries
PLC → Diagnostic/Setting → Operating Mode
  -- CPU should remain in RUN even with OB 86 entries (RSE handles them)

Performance and Memory Budget

Approximate resource consumption on a typical S7-300 / S7-400 with 30 DP slaves and 5 ET 200S stations:

For larger stations (more than 1000 modules) reduce language count and switch FB 126 from cyclic (MODE = 0) to event-driven (default).

Troubleshooting Matrix

Migration Path from STEP 7 V5.x to TIA Portal

1. Migrate the S7 program with the TIA Portal migrator; FB 126 / DB 126 are preserved as system blocks.
2. Re-open the device configuration of the S7-300 / S7-400 station.
3. Re-run System Diagnostics with Report System Errors; the wizard detects the migrated blocks and asks whether to reuse them.
4. Compile the HMI project; the WinCC alarm import is replaced by the integrated TIA alarm mapping.
5. Download, restart, and re-run the verification sequence above.

FAQ