S7-1500T Error 113: Configuring Isochronous Measuring Input on TM

1. Problem Description

A SIMATIC S7-1511T-1 PN controller is configured together with a TM DIDO16x24V technology module to acquire a digital mark signal from a paper web (print-mark / register-mark detection). The user adds a Measuring Input technology object in TIA Portal, wires it to the TM input, and assigns it as the measuring input for a SIMATIC S210 synchronous axis driven by MC_MeasuringInput. The project downloads cleanly, but as soon as the technology object is started the CPU raises technology alarm ErrorID 113 with reaction 8:

"Isochronous mode not possible."

The axis is unable to latch a position, and the paper-mark registration loop never closes. The same configuration works only when the technology object is removed, which proves the alarm is raised by the measuring input itself and not by the drive.

2. Affected Components and Versions

3. Root Cause Analysis

Error 113 in the MC_MeasuringInput context is a technology-object alarm of class configuration error. The Measuring Input TO acquires a position value from a configured encoder or axis at the exact moment the hardware input changes state. The acquisition must be deterministic, i.e. the CPU, the TM module, the drive, and the encoder all share one common time base — the PROFINET isochronous (IRT) cycle.

When the CPU raises 113, the diagnosis routine has detected that one of the following conditions is not satisfied:

1. At least one device on the PROFINET line is not assigned to an IRT domain.
2. The send-clock source of the IRT domain is not the PROFINET interface of the CPU.
3. The TM DIDO16x24V has not been configured as a Sync-Slave with the same send-clock and reduction ratio as the Sync-Master.
4. The S210 is not participating in the same isochronous domain as the CPU (missing IRT slot assignment or wrong telegram).
5. The send clock of the IO device differs from the send clock of the CPU's PROFINET interface (X1).

In the source case, the CPU had been created with the default send-clock generator set to "Local Send Clock" of the TM DIDO16x24V instead of the CPU's PROFINET interface. Because the Measuring Input TO requires the position to be latched in the same bus cycle in which the drive provides its actual position, a non-CPU source breaks the time coherence and the TO refuses to start.

4. Decoding Error 113 and Reaction 8

The technology alarm object exposes the following fields after a failed MC_MeasuringInput.Enable:

Reaction 8 is defined in the S7-1500T Motion Control function manual as: "Stop the technology object with the configured ramp; abort all active commands of this TO." It is the standard reaction for configuration errors that cannot be cleared at runtime.

5. TM DIDO16x24V Module Specifics

The TM DIDO16x24V is a digital I/O technology module that supports both standard digital I/O and the following time-stamped functions:

• High-speed counter (up to 1 MHz, depending on configuration)
• Position detection via hardware latch (TO "Measuring Input")
• Cam output (TO "Output Cam")
• Frequency measurement, period measurement

Each latch-capable input (DI0 / DI1 on the ET 200SP version, DI0..DI3 on the ET 200MP version) can be assigned to a Measuring Input TO. The TM must be:

1. Plugged in a PROFINET station that is part of the IRT domain.
2. Configured as a Sync-Slave in the PROFINET topology editor.
3. Operating with the same send-clock (typically 1.000 ms) and reduction ratio as the Sync-Master (CPU).
4. Configured with a valid I/O address range that the TO can read (hardware-ID assigned automatically when wired in TIA Portal).

6. PROFINET IRT Topology for a Measuring-Input Application

The isochronous data flow for a register-mark application with an S210 axis is a single chain:

If any node is a DCP-only (non-IRT) device, or if the TM module sits behind an unmanaged switch, the CPU cannot guarantee the deterministic latency required for the position latch and the TO raises 113.

7. Step-by-Step Resolution

Prerequisites

• TIA Portal V17 Update 4 or V18 Update 2 installed with the S7-1500T HSP (Hardware Support Package) for the S210 drive.
• The PROFINET topology editor is editable (project not in "Commissioning" mode).
• The CPU and all IO devices have valid IP addresses and device names assigned.

Procedure

1. Open the project in TIA Portal and select the CPU 1511T-1 PN in the device tree.
2. Navigate to Properties → PROFINET interface [X1] → Real time settings → Synchronization.
3. Set the role of the PROFINET interface to "Sync-Master". The role selector is the single most important parameter for a measuring-input application.
4. Set Send clock to 1.000 ms. (Valid values: 0.250 ms, 0.500 ms, 1.000 ms, 2.000 ms, 4.000 ms. S210 and TM DIDO16x24V support 1.000 ms and 0.500 ms.)
5. Under RT class, select IRT (not "RT" or "NRT").
6. Open Topology view and check that the ports between CPU, TM, and S210 are interconnected in the editor. Unconnected ports in the topology view still allow a download, but PROFINET cannot guarantee the IRT bandwidth.
7. Select the TM DIDO16x24V → Properties → PROFINET interface → Real time. Set:
   • RT class: IRT
   • Synchronization role: Sync-Slave
   • Reduction ratio: 1 (matches CPU send clock 1.000 ms)
8. Select the S210 → Properties → PROFINET interface → Real time and apply the same three values.
9. Compile the project (Project → Compile → Hardware (rebuild all)) and inspect the topology warnings. There must be zero warnings on the IRT domain.
10. Download to the CPU. After download, open Online & Diagnostics → PROFINET → Topology on the CPU and verify the status of every port: "OK / Synchronized".
11. Open the Measuring Input TO in the project tree, confirm the Hardware input field points to the correct DI of the TM, and re-compile. The TO configuration tab now exposes a new field Isochronous mode: active (was previously greyed out).
12. Re-run MC_MeasuringInput.Enable from the user program. The error must clear within one bus cycle.

8. Verification

After the corrected configuration has been downloaded, the following checks confirm that the Measuring Input TO is operating isochronously:

1. TO online diagnostics: In TIA Portal, go to Measuring Input → Online & Diagnostics → Status. The Isochronous mode status must read "active / OK" and the Cycle time must equal the PROFINET send clock (1.000 ms).
2. Error list: Open the CPU's diagnostic buffer. There must be no entry with ErrorID 113. The last entry should be "Technology object started successfully".
3. Live bit: The MeasuringInput.Status tag .StatusMeasuringInput (bit 0 of the status word) toggles to TRUE as soon as a rising edge is detected at the TM input.
4. Latched position: Drive the axis at constant speed and feed a square-wave signal into DI0 of the TM. The tag .MeasuredValue1 must update on every rising edge with a position resolution of ≤ 1 µm (encoder dependent).
5. Jitter check: Record 1000 latched values and compute standard deviation. A correctly-configured IRT domain shows jitter < 1 µs. A non-isochronous configuration shows jitter > 100 µs and intermittent misses.

9. Common Pitfalls

10. S210-Specific Considerations

The SIMATIC S210 drive controller (SINAMICS S210) is a hard-IRT device. The following combination is the validated, supported configuration for a measuring-input application:

• Telegram 105 (drive object 1, 16-byte standard) or Telegram 106 (with extended setpoints).
• Send clock 1.000 ms (reduction ratio 1) — the smallest send clock at which the S210 maintains its 16 kHz current controller cycle.
• Encoder evaluation through the drive (drive object 1 is the encoder source), with encoder telegram 81 or 83 selected.

If the measuring input TO is configured against an external encoder instead of the drive, the encoder must be either an ET 200SP TM PosInput (6ES7138-6BA00-0BA0) or an SSI/encoder module that supports IRT and is assigned to the same Sync-Master domain.

11. Source-Clock Reference

The send clock is generated by a single device on the PROFINET line — the Sync-Master. In a S7-1500T project the Sync-Master is the PROFINET interface of the CPU, never a TM, never a CP. The "Local Send Clock" option in the TM DIDO16x24V's properties refers to a self-generated clock the TM can use for non-isochronous high-speed counter operation only. The Measuring Input TO rejects that clock because the drive-side position values are produced on the CPU's clock and cannot be aligned to the TM's local clock.

When TIA Portal reports the topology warning "Send clock source mismatch", the build is allowed to continue but every motion TO on that domain will raise 113 at start-up.

12. Recovery from Error 113

Because reaction 8 keeps the axis enabled and the TO in "STOPPED" state, no fault acknowledge is required. The recovery sequence is:

1. Correct the IRT configuration (Sync-Master = CPU [X1], Sync-Slave = TM, S210).
2. Recompile and download.
3. Cold restart the CPU, or issue MC_Reset on the TO to clear the diagnostic buffer entry.
4. Re-issue MC_MeasuringInput.Enable.

If the error persists after a correct topology, check the PROFINET cable plant: a faulty SFP on the CPU's X1 port, an aged patch cable, or a non-PN-rated cable all degrade IRT jitter to the point where the TO falls back to a non-isochronous state and 113 is raised again.

13. Related Diagnostics and KB References

• Siemens Support Entry 109749263 — S7-1500T Motion Control function manual (covers ErrorIDs 100..199)
• Siemens Support Entry 109817506 — SIMATIC S210 System Manual
• Siemens Support Entry 109973545 — TM DIDO16x24V / TM DIDO16x24V HF function manual
• Measuring input technology object (S7-1500, S7-1500T) — TIA Portal V20 documentation
• Siemens Support Entry 109783434 — PROFINET IRT commissioning checklist