SIWAREX WP321 w_ErrorCode Reference and DR3/DR32 Diagnostics

Overview

The SIWAREX WP321 is a single-channel weighing module (Technology Module, TM) in the SIMATIC ET 200SP distributed I/O system. It acquires the mV/V signal from one or more load cells and exposes weight, status, tare, zero, and diagnostic data to the ET 200SP backplane bus for evaluation in the CPU (S7-1200 or S7-1500). When the module reports a non-zero w_ErrorCode in the standard block WP321S (delivered in the "Ready-for-use" project), the value is sourced from the module's own data/command error register and is the first place an engineer must look.

This reference documents the meaning of w_ErrorCode, its companion variable s_IO_DATA.ERROR_CODE, the relationship to data records DR3 and DR32, and the complete data/command error range 5000-8999. It also documents the load-cell and ADC technology errors 1104 and 1106 that appear in SIWATOOL V7 when physical cells are disconnected.

SIWAREX WP321 Module Identification and Integration

The WP321 occupies one slot in an ET 200SP baseUnit (BU type A0). The relevant identification data is summarised below.

Refer to the operating instructions SIWAREX WP321 Equipment Manual (A5E33715669A-02) for the full device specification and slot rules.

Locating w_ErrorCode in the WP321S Block

The standard block WP321S (used in the "Ready-for-use" example project) exposes the error variable on its instance DB:

• Tag: <WP321S_DB>.w_ErrorCode
• Type: WORD (data/command error code)
• Source: Mirrored from the module's DR 3 / DR 32 return payload or the cyclic w_QV error word
• Range: 0 (no error) or 5000-8999 (data/command errors)

For technology errors (load cell, ADC, calibration, etc.) the engineer should NOT use w_ErrorCode but the operating-mode status structure:

• Tag: <WP321S_DB>.s_IO_DATA.SCALE_STATUS.ERROR — Boolean, set when any technology error is pending
• Tag: <WP321S_DB>.s_IO_DATA.ERROR_CODE — additional error word provided by the block (referenced by the Siemens support response in the originating thread)

Data Records DR3 and DR32

Configuration and process data on the WP321 are exchanged through data records. The two that matter for the present problem are DR3 and DR32.

When the WP321S block (small variant) does not read DR 32, the user will see no entries in OPERATION_ERRORS or DR32.TECHNOLOGICAL_ERRORS even though a technology error is active. This is a documented limitation of the small block, not a module fault. To access the technology-error list, the engineer must either:

1. Use SIWATOOL V7 over the service port, OR
2. Read DR 32 explicitly using WRREC / RDREC (S7-1500) or RDREC (S7-1200), OR
3. Use the full WP321S block variant that polls DR 32 each scan.

Data and Command Error Codes 5000-8999

Data/command errors are returned whenever the module rejects a write to DR 3 (e.g. tare command while in running mode, or service-mode command without the correct privilege). The general list is reproduced from the SIWAREX WP321 Equipment Manual and the TIA Portal cloud documentation entry for the module's message list.

The codes above are the canonical Siemens numbering; the WP321S block passes them straight through to w_ErrorCode. If you observe w_ErrorCode = 0 while a hardware fault is present, the error is a technology error, not a data/command error, and you must check the sources listed in the next section.

Technology Errors: Load Cell and ADC (1104, 1106, ...)

Technology errors are signalled through DR 32 and through s_IO_DATA.ERROR_CODE; they are NOT shown in w_ErrorCode. The most common field codes are:

When you physically disconnect a load cell, two effects occur simultaneously: the bridge becomes unbalanced (1104 ADC sens voltage too low) and the resulting force measurement falls below the lower limit (1106 Load cell underload). Both codes are visible in SIWATOOL V7 but neither is reflected in w_ErrorCode.

Status Structure s_IO_DATA and SCALE_STATUS

The full s_IO_DATA UDT carries the diagnostic and process status. The relevant members are:

The Siemens support recommendation in the originating thread is explicit: "When you disconnect the cells, you have to check the bit s_IO_DATA => SCALE_STATUS => ERROR." This bit latches until the error condition is removed and the operator acknowledges the error using DR 3 command 0x0200 Acknowledge error.

Diagnostic Procedure Step-by-Step

Use the following sequence when the field device reports a non-zero w_ErrorCode or a lit SCALE_STATUS.ERROR:

1. Verify power and grounding. Measure 24 V at the BU type A0 base unit; verify the PE/functional-earth connection at the load cell junction box.
2. Check the ET 200SP station diagnostic buffer. Open TIA Portal → Online & Diagnostics → Diagnostic buffer. The module slot will identify PROFINET, channel, or module-level faults that do not surface in w_ErrorCode.
3. Inspect w_ErrorCode. If 5000 ≤ w_ErrorCode ≤ 8999, this is a data/command error — jump to the table above and resolve from the DR 3 command that triggered the error.
4. Inspect s_IO_DATA.SCALE_STATUS.ERROR. If TRUE, read the technology-error list. With the small WP321S block that does not poll DR 32, launch SIWATOOL V7 to see the codes (e.g. 1104, 1106).
5. Localise the cell fault. Disconnect each cell in turn. If removing a single cell clears the 1104/1106, the fault is in the cell or its wiring harness. If the error remains with all cells removed, swap the load-cell cable for a known-good one. If the error remains with a calibration resistor across the WP321 terminals, the module is the fault.
6. Verify Service mode is ON before any DR 3 calibration command. Send DR 3 command 0x0102 (Service on) and confirm SCALE_STATUS.SERVICE_MODE = TRUE.
7. Recalibrate. Perform zero set and span adjustment with calibrated test weights. Monitor the technology-error list — it should remain empty.
8. Acknowledge and clear. Send DR 3 command 0x0200 to clear the latched errors. Confirm SCALE_STATUS.ERROR = FALSE and w_ErrorCode = 0.

TIA Portal Configuration Reference

For the data/command errors to propagate to w_ErrorCode, the WP321S block must be configured with:

• Hardware identifier of the WP321 module (set in the module's properties → "Module parameters")
• Input / output addresses consistent with the PROFINET configuration
• Command output enabled (DR 3 write allowed)
• DR 32 read explicitly enabled if you want technology errors to appear in the block's diagnostic structure; otherwise they will be visible only in SIWATOOL V7

The standard block supports both S7-1200 and S7-1500 CPUs. Note that on the S7-1200, RDREC/WRREC must be called from an organisation block that is not OB1 if the slot is on a high-speed PROFINET network; the WP321S block handles this internally.

SIWATOOL V7 Error Display

SIWATOOL V7 connects to the WP321 over the front-panel USB service port and exposes the full technology-error and operating-error lists regardless of whether the small WP321S block is being used. This makes SIWATOOL V7 the single best diagnostic tool when the block is silent.

Procedure:

1. Connect a USB cable between the PC and the WP321.
2. Launch SIWATOOL V7, choose COM port, and connect.
3. Navigate to Diagnostics → Error list. The active technology errors (e.g. 1104, 1106) and the operating-mode errors are both shown.
4. Use Service → Acknowledge errors to clear latched errors after the physical cause is fixed.

Error Code Mapping and Troubleshooting Matrix

The following matrix maps the most frequent field conditions to the variable you should read first and the typical code you should expect.

Commissioning and Verification Checklist

• [ ] Module firmware on the device matches the HSP in TIA Portal (no Firmware-update required / Firmware-update required warning).
• [ ] Slot, baseUnit (BU type A0), and shield contact carrier are mechanically correct.
• [ ] Load cells wired per the manual (4-wire or 6-wire) and the sense jumpers in the junction box are installed.
• [ ] Service mode toggled ON before any DR 3 calibration command.
• [ ] w_ErrorCode = 0 after every successful DR 3 write.
• ] s_IO_DATA.SCALE_STATUS.ERROR = FALSE after the acknowledge command.
• [ ] DR 32 read returns 0 in the technology-error list after the acknowledge command.
• [ ] SIWATOOL V7 error list is empty after a full warm-up with the process load applied.
• [ ] Test weight verification: 0%, 25%, 50%, 75%, 100% of nominal load all within tolerance.

Field-Proven Caveats

• The small WP321S block from the "Ready-for-use" project deliberately does not read DR 32. If you depend on technology-error propagation to the PLC, switch to the full WP321S block variant or add an explicit RDREC on DR 32.
• Codes 5004 (Service mode required) and 5020 (parameter assignment error — data record not applied) are the two most common reasons for an apparently "stuck" calibration. They are not hardware faults.
• Codes 1104 and 1106 appear together whenever a cell is disconnected. Use them as a single diagnostic signature, not as two independent faults.
• On multi-cell installations, use a calibration resistor across the WP321 input terminals to confirm that the module itself is healthy. If the technology-error list clears with the calibration resistor in place, the module is good and the fault is in the cell, wiring, or junction box.
• The block's ERROR_CODE and the module's w_ErrorCode are different variables; the module's w_ErrorCode reports only data/command errors, while the block's ERROR_CODE can carry additional internal status.

FAQ