Resolving Siemens IM151-1 Error 13:4565 PROFIBUS Byte Limit

Resolving Siemens IM151-1 Error 13:4565 PROFIBUS Byte Limit

Field diagnosis of a 244-byte PROFIBUS slave budget violation on the ET 200S IM 151-1AA04 interface module, with module-by-module byte accounting, three configuration recovery paths, and verification steps for the commissioning engineer.

1. Problem Statement: Decoding Error 13:4565

When a SIMATIC ET 200S station is built around an IM 151-1 PROFIBUS interface module (catalog number 6ES7 151-1AA04-0AB0) and the configured I/O exceeds the slave's process-image budget, the master CPU—commonly a S7-300 or S7-400—reports a diagnostic entry whose event identifier is 13 and whose associated code is 4565. The full text rendered by STEP 7 in the diagnostic buffer reads:

"The maximum data length of parameterizing the slave with the address PROFIBUS 2"

Operators see the error surface immediately on online connection. The slave drops off the bus, the SF (group fault) LED on the IM 151-1 lights red, and the process image is no longer refreshed. Crucially, the error is not a wiring or termination problem—cable integrity and PROFIBUS addresses may be perfectly valid. The cause is structural: too many bytes have been assigned to the slave.

2. Affected Hardware: ET 200S IM151-1 Interface Module

The IM 151-1AA04 is the PROFIBUS DP interface module (head station) of the SIMATIC ET 200S distributed I/O system. It is mounted on a DIN rail and acts as the DP slave on the PROFIBUS network. The base unit hosts the PROFIBUS D-sub connector and a row of TM-E or TM-P terminal modules into which electronic modules are inserted.

The 244-byte limit is the binding constraint. It is the same ceiling imposed on any PROFIBUS DP-V0/V1 slave, and the IM 151-1 family does not expose an extended mode. ET 200S stations that exceed 244 input or 244 output bytes cannot be parameterized by the DP master, regardless of firmware version.

For an overview of indicator LED meanings (SF / MT / ON) on the related IM 151-8 PN/DP CPU interface, refer to the Siemens Industry Online Support page: Status and error displays of the IM 151-8 PN/DP CPU interface module. The LED philosophy is identical across the ET 200S IM 151-x family.

3. Root Cause: PROFIBUS Slave Address Space Budget

PROFIBUS DP uses a per-slave parameterization frame at startup. The master uploads the Set_Param telegram defining the number of input and output bytes the slave must handle. If the requested length exceeds the slave's published maximum (244 bytes for IM 151-1), the slave rejects the parameterization and reports back to the master as "station failure." STEP 7 then displays the diagnostic buffer entry 13:4565.

The same limit applies independently to inputs and outputs:

• I_total = Σ bytes requested by every input module in the station ≤ 244 bytes
• Q_total = Σ bytes requested by every output module in the station ≤ 244 bytes

A station may simultaneously have 244 input bytes and 244 output bytes for a 488-byte aggregate process image, but each direction is capped individually. Forgetting this asymmetry is the most common source of the error after a single direction is filled.

Worked example from the field case: an ET 200S was built from 9 DI channels, 5 DO channels, 15 AI modules, and 5 AO modules. Counting the input direction only:

• 9 DI channels → packed into the byte budget as 2 bytes (the 9th bit occupies a fresh byte)
• 15 AI modules → 15 × 16 bytes = 240 bytes (each high-resolution 2AI module claims 16 bytes for value + status)

I_total = 2 + 240 = 242 bytes by the conservative count, or 249 bytes if the digital bytes are rounded up to 9. The output direction (5 DO + 5 AO) is independent and is well within its own 244-byte budget. The DP master is told that the slave needs more than 244 input bytes; parameterization fails; error 13:4565 is logged.

4. ET 200S I/O Module Address Footprint Reference

The byte consumption of an ET 200S module is determined by STEP 7 at hardware configuration time and is not editable. Use the following reference for the most common module families. The order numbers are the standard catalog numbers; check the ET 200S system manual for the exact variant installed in your plant.

The 16-byte footprint of the 4MB02-0AB0 analog input module is the most common source of 13:4565 in process plants. Each module reserves 8 bytes per channel for the IEEE 754 floating-point representation and 8 bytes per channel for value status; STEP 7 cannot be coerced to compress them. To keep a high channel count under 244 bytes, mix 4MB02 modules with 4GB01/4GB52 modules:

Bytes_used = N_highres * 16 + N_standard * 4
244        = N_highres * 16 + N_standard * 4

where N_highres and N_standard are counts of 2-channel modules.

5. Step-by-Step Diagnosis

When 13:4565 appears in the diagnostic buffer, follow the procedure below to confirm the byte-budget diagnosis before touching the configuration.

1. Open STEP 7 and go online with the DP master CPU.
2. Navigate to PLC → Diagnostic/Setting → Diagnostic Buffer and read the entry text. Verify the wording matches "maximum data length of parameterizing the slave with the address PROFIBUS n."
3. Open the hardware configuration (HW Config) for the project. Right-click the IM 151-1 station and select DP Slave Properties → Configuration. The I-addresses and Q-addresses tabs list the start address and length of the slave in the master process image. Note the total input length (L) and output length (L').
4. Cross-check: L ≤ 244 and L' ≤ 244. If either is > 244, the diagnosis is confirmed.
5. If L and L' are within 244 but you still see the error, click Station → Check Consistency in HW Config. STEP 7 will surface any module that contributes more than its catalogue footprint, often a custom GSD import.
6. Read the slot table: in HW Config, every module is listed with its address range. Sum the address spans slot-by-slot to confirm the budget manually:

   I_bytes_total = sum(addr_end_i - addr_start_i + 1) for i in slots
   Q_bytes_total = sum(addr_end_q - addr_start_q + 1) for q in slots

7. If a single module (typically the 4MB02 analog input) is the dominant consumer, plan to reduce the count or replace it with a 4-byte module.

6. Resolution Strategy A: Reduce the I/O Count

For the field case (9 DI + 5 DO + 15 AI + 5 AO) the cleanest fix is to drop one high-resolution AI module. Recalculating:

I_bytes = 14 * 16 (AI) + 2 (DI packing) = 226 bytes  ->  within 244

The trade-off is a single lost measurement channel. When this is acceptable, the procedure in HW Config is:

1. Right-click the rightmost AI slot in the ET 200S station.
2. Select Delete and confirm.
3. Re-run Station → Check Consistency in HW Config.
4. Save and recompile, then download the hardware configuration to the master CPU.

For plants that cannot lose a channel, replace one 6ES7 134-4MB02-0AB0 with a 6ES7 134-4GB52-0AB0. The 4GB52 module returns 4 bytes per module (2 channels × 2 bytes IEEE 754). The byte budget becomes:

I_bytes = 14 * 16 + 1 * 4 + 2 (DI) = 230 bytes  ->  within 244

The electrical resolution drops from the 4MB02's high-precision range (15-bit + sign + sign of life) to the 4GB52's 16-bit range, but most process measurements (level, pressure, temperature with standard probes) fit comfortably in 16 bits.

7. Resolution Strategy B: Re-Architect the Station

When the application truly needs all 36 modules, split the ET 200S station into two DP slaves. Two IM 151-1 heads on the same PROFIBUS segment each carry their own 244-byte budget, doubling the aggregate process image to 488 input bytes (and 488 output bytes).

Topology sketch:

The implementation steps in HW Config:

1. Insert a second PROFIBUS station on the same DP master system. Assign a unique PROFIBUS address (e.g., slave 2 keeps address 2; the new slave takes address 3).
2. Move the displaced modules to the new station. Distribute the I/O so each station stays under 244 bytes in each direction.
3. Update the symbol table and any FB/FC logic that references the moved addresses.
4. Download and run Check Consistency on both stations.

When the cabinet already has the wiring for a single station, splitting it physically is invasive. A non-invasive alternative is a PROFIBUS DP/PA segmenter (e.g., a Siemens DP/PA coupler or a Link) that places a second DP-V1 island on the same master. The master sees two slaves, each with a 244-byte budget, but only one DP segment exists in the cabinet.

8. Configuration in STEP 7 / TIA Portal

After applying one of the resolution strategies, recompile the hardware configuration. In STEP 7 V5.x:

1. Open HW Config for the master station.
2. Click Station → Check Consistency. Resolve any reported conflict before continuing.
3. Click Station → Save and Compile. The compilation log lists the total I bytes and Q bytes per slave. Verify the numbers against the 244-byte ceiling.
4. Download to the target (PLC → Download to Target → Selected Target). STEP 7 prompts you to overwrite the hardware configuration; confirm.
5. Restart the CPU in RUN-P or perform a STOP→RUN transition so the new parameterization telegram is sent to the IM 151-1.

In TIA Portal (V13 SP1 and later with the ET 200S HSP):

1. Open the Device view of the DP master.
2. Right-click the ET 200S slave and choose Properties → Configuration. The "Module parameters" tab shows the address layout.
3. Use the "Compile" command (Project tree → right-click device → Compile). Compilation errors surface in the Inspector window.
4. Download the project to the CPU. TIA Portal transfers hardware and software together.

Sample diagnostic block logic to surface 13:4565 to a WinCC HMI alarm:

// OB1 - Cyclic diagnostic fetch
CALL  "DP_DIAG"           // FB 125 or RDREC/SFB 52
     REQ     := TRUE
     LADDR   := W#16#1000  // Diagnostic address of IM 151-1 (slot 0)
     RET_VAL := MW100
     BUSY    := M101.0
     DIAG    := P#M120.0 BYTE 16

// Local tags
L     DB125.DBD0          // Slot 0 standard diagnostic
L     W#16#0D45           // 0x0D45 == 13:4565 high/low
==I
S     "Alarm_13_4565"

The diagnostic address of the IM 151-1 is configured in the DP slave properties; by default it is one byte above the input area. The example above uses W#16#1000 as a placeholder; replace with the actual diagnostic address from the project.

9. Verification and Commissioning Checks

After downloading the corrected configuration, run the following checks before signing off the change:

1. Diagnostic buffer clean. The CPU's diagnostic buffer should not contain any new 13:xxxx entries. Clear the buffer with PLC → Diagnostic/Setting → Clear and force a STOP→RUN transition. If a 13:4565 re-appears, the byte budget is still violated.
2. SF LED off. The red SF (group fault) LED on the IM 151-1 must be dark. A lit SF LED combined with a clean CPU buffer indicates a slave-local diagnostic; resolve it before relying on the station.
3. BF LED off. The red BF (bus fault) LED on the IM 151-1 must be dark. BF flashing at 0.5 Hz means the master is not addressing the slave; verify PROFIBUS address and termination.
4. Process image update. In STEP 7, open PLC → Monitor/Modify and inspect a few input and output bytes. Confirm the values follow the physical signals.
5. Watchdog test. Disconnect the PROFIBUS connector for 3 seconds and reconnect. The IM 151-1 must rejoin the bus within 5 s (DP-V1 re-parameterization). A re-parameterization failure with the same 13:4565 message confirms the budget is still violated.
6. Margin check. I_bytes_total and Q_bytes_total should be at least 16 bytes below 244 to allow for future module additions. If you have just barely fit, document the limit in the project change log.

10. Common Pitfalls and Adjacent Limits

The 244-byte PROFIBUS budget is one of four hard limits on an ET 200S station. Engineers often confuse them, so document each one explicitly in the design phase:

Pitfalls seen in the field:

• Misreading the master process image size. Some S7-300 CPUs cap the process image at 1024 bytes total. A station that fits the slave budget may still be clipped by the master image. STEP 7's compilation log will warn when an address falls outside OB1's process image (PII/PIQ).
• TIA Portal auto-mapping. TIA Portal's device view auto-arranges modules in slot order. Re-ordering to put the high-byte modules first can shift the cumulative total and may make the configuration pass when the same modules in a different order would fail. The total is independent of order, but the diagnostic error message is slot-ordered.
• Custom GSD imports. A GSD-imported third-party slave on the same master does not affect the IM 151-1 budget. The 244-byte limit is per-slave. However, a GSD slave with its own internal modules may claim bytes through a DP-V1 expanded telegram, and the master will refuse parameterization if the total exceeds the master's published max_sap_count. This is a separate, less common, error code.
• Hot-swapping a module. Replacing a 4MB02-0AB0 with a 4GB52-0AB0 in the running station is allowed by ET 200S, but the new module has a different STEP 7 catalog footprint. The CPU's diagnostic buffer will log the configuration mismatch until HW Config is updated and downloaded. Plan a maintenance window.
• Power budget, not data budget. Each AI module draws current from the 24 V power bus. The 4MB02 module draws ~150 mA from the backplane. A 15-AI station easily exceeds the IM 151-1's 5 A power bus budget and requires one or more PM-E (power module) inserts. This is a different limit but is often hit in the same station that triggers 13:4565.

For the broader ET 200S family and the related IM 151-8 PN/DP CPU's LED meanings, the Siemens Industry Online Support entry Status and error displays of the IM 151-8 PN/DP CPU interface module provides a useful side-by-side. Note that the IM 151-8 PN/DP is a different model (with PROFINET and an integrated CPU); the byte limits remain the same PROFIBUS DP ceiling when the IM 151-8 PN/DP is used as a slave on a DP segment.

11. Frequently Asked Questions