Simovert MC to Sinamics S120 Migrating P172/P173 Position Sensing

Overview

The Simovert Master Drive MC (6SE70 / 6SE71 series) exposes two BICO parameters that allow a higher-level controller (typically a SIMATIC S7 PLC) to overwrite the actual position value of the drive and to command the moment of the overwrite:

• P172 – BICO selector for the connector that supplies the position setting value (LU, length units).
• P173 – BICO selector for the binector (digital command) that enables the position setting.

When a Simovert MC drive is replaced by a SINAMICS S120 (typically with a CU320-2DP / CU320-2PN Control Unit and a SIMOTION- or S7-supplied setpoint), the same functional behavior must be reproduced on the S120 platform. On SINAMICS S120 the equivalent function is implemented through the position actual-value conditioning block, controlled by p2514 and p2515 (function diagrams 4010 and 4720 in the SINAMICS S120/S150 List Manual).

This reference is written for engineers migrating an aluminum-strip puller drive (Simovert MC → SINAMICS S120) with an S7-300 (CPU 315-2DP) acting as the position master and the external encoder wired directly to the PLC. It documents the BICO equivalents, the meaning of the four indexes in p2514 / p2515, the wiring through the Sensor Module in slot C, and the verification steps required at commissioning.

Prerequisites

1. Replacement drive: SINAMICS S120 with a CU320-2DP Control Unit (firmware ≥ V4.4 recommended; V5.x for current S120 commissioning) and a Sensor Module SMC20 / SME20 / SMC40 installed in slot C of the line module / Motor Module. The motor encoder is connected to this module.
2. Position controller: SIMATIC S7-300 with CPU 315-2DP (PROFIBUS DP master). The PLC already reads the external encoder (incremental or SSI/EnDat) and computes a 32-bit LU position value in the same coordinate system as the Simovert MC.
3. Commissioning tool: SINAMICS STARTER (for firmware ≤ V4.x) or SINAMICS Startdrive in TIA Portal (for V5.x projects).
4. Documentation: SINAMICS S120/S150 List Manual (function diagrams 4010, 4720) and the SINAMICS S120 Function Manual (basic positioner / position actual-value conditioning chapter).
5. Encoder slot knowledge: in S120 the encoder interface is selected by p0400[0..n] (encoder type) and the indexing of the encoder data set by the data-set selection word. The Motor Module's slot C in the S120 topology corresponds to the Sensor Module physically inserted at the Motor Module (X520 / X521 / X522). On a CU320-2DP topology view in STARTER, slot C is the Sensor Module of Drive Object SERVO / VECTOR encoder interface 1 (encoder 2 if two encoders are used).

Slot-C Encoder on Simovert MC vs SINAMICS S120

The phrase "position sensing for motor encoder in slot C" in the original Simovert MC documentation refers to the encoder interface slot on the MC option board. On a 6SE70/6SE71 MC the option slots are labeled A, B, C, D, E, F. The motor-mounted encoder that closes the position loop is normally wired to the encoder option board in slot C; the position actual value is taken from this interface, optionally after evaluation of the resolver / TTL / HTL / SSI signals.

On SINAMICS S120 the slot concept is replaced by the drive object (DO) topology:

Meaning of P172 and P173 on the Simovert MC

P172 and P173 are BICO selectors, not direct process-data sources. They are documented in the Simovert MC Compendium (file mc24_kompend_e.pdf, available on the Siemens Industry Online Support portal).

• P172 – Setting value (LU): a BICO output of type "double word / 32-bit connector". The drive reads the connector selected by P172 and uses it as the new position actual value. Typical sources on the Simovert MC: connector from a free analog input, from a peer-to-peer PROFIBUS PZD, or – in puller applications – from the PLC via a peer-to-peer word.
• P173 – Setting command: a BICO input of type "binector" (1-bit digital). When the selected binector transitions to 1 the drive latches the value of P172 into the position actual value. A typical source is a digital input, a control word bit, or a peer-to-peer bit. In the source application a dedicated bit from the S7-315-2DP triggers the latch.

The two parameters together implement an edge-triggered position actual-value preset: on the rising edge of P173, the connector value of P172 is loaded into the position actual value and used as the new reference. After the trigger the drive continues to integrate its encoder increments; P172 / P173 are only used to pre-set the value, not to override it continuously.

SINAMICS S120 Equivalent: p2514 and p2515

The migration mapping is:

The reversal of naming (the S120 "signal" parameter is p2515 while the MC "signal" parameter is P172) is the most common migration error – double-check the index and the function diagram before wiring.

Indexing of p2514 and p2515 (0…3)

Both p2514 and p2515 are indexed with four entries. The indexes correspond to the position actual-value conditioning stages and the available triggers inside the basic positioner (EPOS). For most puller applications only index 0 is used; the additional indexes cover second encoder, position-tracking switchover and advanced EPOS functions. The exact meaning is given in function diagram 4720 of the S120 List Manual:

Wiring the BICO Chain on the S120

1. Open the S120 project in STARTER / Startdrive and navigate to the drive's Position control / Position actual-value conditioning screen.
2. Set p2515[0] to the connector that carries the PLC-supplied position value. In a typical PROFIBUS DP peer-to-peer wiring this is the connector on a Telegram extension word, e.g. BI: p2051[x] / CI: p2060[x] of the S120 receive word that carries the LU value. The exact receive-word index depends on the telegram configuration (standard telegram 6 / 7 / 9x, supplementary telegram 999).
3. Set p2514[0] to the binector that carries the trigger bit from the PLC. Typical source: r2090.x (bit of the received PZD), or a digital-input bit r0722.x if a hardware line is used as the trigger.
4. Enable the position controller and ensure the drive is in the correct operating mode (e.g. p1300 = 21 for closed-loop position control with encoder on motor).
5. Set p2521[0] (output) only for monitoring; the value should track r0479 (raw encoder actual) plus the preset value loaded by p2515.

Example: S7-300 → S120 PROFIBUS PZD

If the S7-315-2DP sends a 32-bit LU value in PZD words 6/7 and the trigger bit in PZD word 8 bit 0, the STARTER / Startdrive wiring is:

CI: p2515[0] = r2050[4]   (PZD word 6+7 of the receive telegram, double word connector)
BI: p2514[0] = r2090.0   (bit 0 of PZD word 8, binector)

On the S7 side the bit must be set to 1 for at least one PROFIBUS cycle and then reset by the PLC; the drive latches the LU value on the rising edge of r2090.0.

Puller-Specific Commissioning (Aluminum-Strip Application)

A puller in an aluminum rolling / finishing line imposes the following requirements on the actual-value preset function:

• Stable tracking of strip position between the entry bridle and the exit coiler without cumulative slip error.
• On threading (strip entering the puller rolls) the position actual must be reset to a defined value to avoid a step in the position-loop setpoint.
• On coiler-change the position actual must be shifted by the circumference of the new coil so that the downstream tension controller keeps operating in continuous mode.
• The trigger events are typically generated by the S7-300 from digital inputs (e.g. strip-in photo-eye, tail-out sensor, coiler-1-full limit switch).

Implementation steps:

1. Set the linear scale of the position actual to LU (1 LU = the resolution that matches the PLC's external encoder). This is done by the load gear p0432 / p0433 (rotary) and the LU scaling parameters p0112 / p0113 or, in the EPOS section, p2530 / p2531.
2. Configure p2514[0] and p2515[0] as documented above.
3. Configure the S7-300 to write a new LU value to PZD 6/7 and a 1-cycle trigger to PZD 8.0 whenever a strip-in or coiler-change event is detected.
4. Verify in STARTER / Startdrive trace that r2521[0] jumps to the new value on the trigger edge and continues to track the motor encoder without further intervention.

Verification

After BICO configuration, perform the following checks before putting the puller into production:

1. Open the STARTER / Startdrive trace and record r2521[0], r2050[4] and r2090.0 for 10 s.
2. Force p2514[0] to "1" and observe whether r2521[0] takes the value of r2050[4].
3. Reset p2514[0] and rotate the motor by hand: r2521[0] must increment in the correct direction (sign of p0410).
4. Re-trigger: r2521[0] must jump back to the value of r2050[4] without overshoot or oscillation.
5. Read r2521[1]…r2521[3] – they must be 0 or track the second encoder (depending on indexing of p2514/p2515). A non-zero value on an index that is not in use usually indicates a leftover BICO wiring from a previous project.

Troubleshooting Matrix

Differences vs. the Simovert MC that Migrators Must Know

• Parameter numbering – the MC uses 3-digit P-numbers (P172, P173); the S120 uses 4- or 5-digit p-numbers (p2514, p2515). Tools and scripts must be updated.
• BICO model – both platforms use the same BICO concept (connectors / binectors) but the S120 has many more parameters and a stricter typed BICO. A wrong-type assignment in STARTER will be rejected with F08501 (BICO error).
• Indexing – the MC exposes a single P172 / P173 pair; the S120 exposes p2514[0..3] / p2515[0..3]. A "first-time" commissioning must explicitly write index [0]; STARTER does not implicitly propagate the value to the other indexes.
• Function diagrams – on the MC, the position-setting path is in diagram G188 (Compendium). On the S120 the equivalent diagrams are 4010 (position actual-value conditioning) and 4720 (EPOS / basic positioner). The S120 List Manual page 1015 referenced in the field report is the EPOS / preset section.
• Trigger edge – the MC accepts a level (P173 = 1) and a falling edge reset; the S120 uses a positive-edge-sensitive trigger (p2514 changes from 0 to 1) and requires the trigger binector to be reset before another preset is accepted.
• Slot C as hardware – on the MC, slot C is a physical option slot. On the S120 the Sensor Module in slot C of the Motor Module is a separate hardware module addressed by DRIVE-CLiQ; a faulted module produces F013xx or F085xx and the position preset function will not work until the module is replaced.

Migration Checklist

1. Document the BICO source of the original P172 (connector) and P173 (binector) on the Simovert MC. This is mandatory because the same source must be used on the S120 to keep the PLC program unchanged.
2. Order the S120 Motor Module and Sensor Module so that the slot-C encoder interface is physically available (SMC20 for incremental, SME20 for EnDat, SMC40 for SSI).
3. Update the S7-300 hardware configuration: keep the I/O addresses of the external encoder (the PLC remains the source of the LU value), add the S120 as a new PROFIBUS DP slave with the correct GSD (SIEM8170) and the same telegram length as the MC replacement.
4. Import the S120 commissioning archive into STARTER / Startdrive and configure p2514[0] / p2515[0] according to the MC BICO source list.
5. Run a trace on r2521[0] and confirm the preset behavior end-to-end.
6. Sign off the migration with a strip-threading test on the actual puller and a coiler-change test with the coil diameter signal from the S7.