SINAMICS S110 with S7-1200: Speed Control with Length Counter Setup

This technical reference covers a complete commissioning workflow for a SINAMICS S110 servo drive (CU305DP control unit) driving a 1FK7042 synchronous motor through a S7-1214C controller. The application is a band-pulling line that must run under closed-loop speed control, accumulate material length in a resettable counter, and surface drive faults, status, and safety information to the PLC for HMI alarming and trending.

Two parallel control paths are documented: the recommended basic positioner in JOG mode with override path, and the alternative ramp generator path with a position controller that is engaged only on demand. A real-world safety caveat documented in the field is highlighted: enabling the drive while the position setpoint is at zero and the actual position is non-zero causes the position controller to demand a step change that the drive will accelerate to follow, generating an unintended jerk on the band. The procedure below explicitly prevents this condition.

1. System Architecture

The S7-1214C exchanges cyclic process data with the S110 over PROFIBUS DP (or PROFINET when using CU305PN). The telegram in both directions must match. A free telegram 999 with BICO extension is also supported and is the right choice when you need length, status, and safety in one PZD frame.

2. Prerequisites

• S7-1214C CPU (any DC/DC/DC or DC/DC/RLY variant) with at least firmware V4.2 for full PROFIdrive conformance. Higher firmware V4.4 or V4.5 is recommended for HSC improvements.
• SINAMICS S110 with CU305DP control unit, firmware 4.7 SP3 or 5.2 (STARTER commissioning tool ≥ V5.4 or Startdrive in TIA Portal V17+).
• 1FK7042-xAF7x servo motor (Drive-CLiQ interface built in).
• PROFIBUS DP cable with D-sub connectors; PROFINET cable if a CU305PN is fitted.
• Length-sensing encoder (incremental, 24 V HTL or TTL) wired to the HSC inputs Ia0/Ia1 of the CPU, or to a TM PTO module if you run the counter on a signal module.
• TIA Portal V17 or later for SIMATIC S7-1200; STARTER or Startdrive for the S110 commissioning.
• Optional: CM 1241 RS485 if you use the USS-based positioning reference approach as a fallback path.

3. Telegram Selection in SINAMICS and S7-1200

The PLC and drive must use the same standard PROFIdrive telegram on both sides. The available telegrams for S110 in this hardware configuration are:

Recommendation for this application: use telegram 110 when the basic positioner is active, or telegram 4 when the drive is configured as a pure speed follower. Telegram 110 carries G1_XIST_A, the 32-bit cyclic position actual value, which doubles as the length counter source if the motor encoder is mechanically coupled to the band roller. If you need torque and warning codes, switch to 9, 390, or 391. The free telegram 999 is the right choice when none of the standard telegrams fit the application because the setpoint and actual layout are mismatched with the available signals.

4. Configuring SINAMICS S110

4.1 Drive commissioning (STARTER / Startdrive)

1. Open the S110 project offline and perform the online/offline comparison so the actual topology loads.
2. Run the drive configuration wizard, accept the Drive-CLiQ topology, and confirm the 1FK7042 motor data (parameter p0301) matches the nameplate.
3. Set the control mode to speed control with position controller as function module:
   p1300[0] = 21 (speed control with torque limit)
   or, for the basic positioner path:
   p1300[0] = 11 and p10800 = 1 (basic positioner active).
4. Configure telegram to match PLC:
   p922 = 110 for EPOS, or
   p922 = 4 for pure speed control.
5. Set JOG setpoints:
   p2585 = JOG1 speed (e.g. 1500 rpm)
p2586 = JOG2 speed (e.g. 300 rpm)
p2640 = JOG acceleration (e.g. 200 rpm/s)
p2641 = JOG deceleration (e.g. 200 rpm/s).
6. Enable the position controller as a function module only when traversing. Right-click the axis in STARTER → Function modules → tick Position controller. Leave the ramp generator active in normal operation, switch to position controller only on demand.
7. For length counter reset: parameter p29220 (set actual position) accepts a trigger from a digital input wired to the reset pushbutton, or a BICO source from STW bit-driven control word.
8. Save the project to ROM and copy RAM to ROM after each parameter change.

4.2 Speed override path (basic positioner, JOG mode)

The basic positioner runs the motor in JOG mode with p2585 as the JOG1 reference velocity. The override is applied through the dedicated input p2646 (JOG override) in the range 0–100 % and is gated by the active JOG setpoint select bits in STW1 bits 8/9. The PLC can write a 16-bit word to NSOLL_B in telegram 110 and let the basic positioner close the loop on its own ramp generator, or it can command velocity directly via NSOLL_A/B with override scaling. This is the cleanest path for a band-pulling line because the basic positioner's ramp generator replaces a hand-coded ramp function in the PLC.

4.3 Ramp generator path (alternative)

If the position controller must remain active in the background for a future indexing operation, configure the ramp generator as the active setpoint source and treat the position controller as a function module that is engaged by control bits. The drive ramps up to the demanded velocity with p1120 (ramp-up) and p1121 (ramp-down), and the position controller is enabled only when bit 13 of the extended control word (STW2 bit 13) is set. To return to speed control, clear the bit and the ramp generator takes over. This path is workable but adds switching logic; the JOG-with-override path is preferred.

5. Configuring the S7-1200 PLC

5.1 Hardware configuration

1. Add the S7-1214C to the TIA Portal project. Confirm the article number, e.g. 6ES7214-1AG40-0XB0 for DC/DC/DC.
2. Insert the SINAMICS S110 device from the catalog (HSP for STARTER exported GSD) and assign the PROFIBUS address to match the rotary switches on the CU305DP, typically 3 or 4 for the first drive.
3. Right-click the drive device → Properties → Telegram configuration and select the same telegram as the drive (110 for EPOS, 4 for speed).
4. Map the cyclic PZD into a data block, for example DB_Drive with the first 12 bytes as the receive area and the next 12 bytes as the send area, or use process image tags directly.

5.2 Telegram structure for telegram 110

5.3 STW1 bit assignment (key bits)

5.4 ZSW1 key bits

6. Length Counter Implementation

There are two viable sources for the length counter. The cleanest is the SINAMICS S110's G1_XIST_A cyclic position actual value (telegram 110, PZD offset 6–7, 32-bit signed). It is updated every PROFIdrive cycle and is already in motor revolutions, which you can scale by the roller circumference to get millimetres. The alternative is a discrete encoder on the band roller, fed into an S7-1200 high-speed counter.

6.1 Reading G1_XIST_A in SCL

// DB_Drive layout (10 PZD words = 20 bytes per direction)
// Bytes 0..1  : ZSW1  | 2..3  : ZSW2  | 4..5 : G1_ZSW
// 6..7 : G1_NIST_B  | 8..11 : G1_XIST_A | 12..13 : MIST | 14..15 : ZSW3
// 16..17 : FAULT_CODE

// Length counter using SINAMICS position actual
"DB_Length".PosActual_LU   := "DB_Drive".G1_XIST_A;        // load units
"DB_Length".PosActual_mm   := "DB_Length".PosActual_LU
                                * "DB_Length".LU_to_mm_factor;

// Reset condition: HMI button OR digital input
IF "DB_Length".CmdReset OR "I_LengthReset" THEN
    "DB_Length".PosActual_mm   := 0;
    "DB_Length".PosActual_LU   := 0;
END_IF;

To reset G1_XIST_A in the drive, set bit 4 of G1_STW (set actual position) and write the desired position in the next telegram. The drive applies the new actual position on the next cycle. The basic positioner also supports p29220 as a BICO target to perform the same reset from a digital input on the CU305DP.

6.2 S7-1200 High-Speed Counter fallback

When a separate length encoder is mounted on the band roller, configure an HSC on the CPU. The S7-1214C supports up to 6 HSC instances (HSC 0..5). Wire the encoder to Ia0 (A) and Ia1 (B) for quadrature, which gives 4x the pulse count.

The HSC is configured in the CPU properties under High-speed counters (HSC). The relevant configuration follows the S7-1200 high-speed counter configuration in the TIA Portal manual collection.

The HSC is initialized once with the CTRL_HSC instruction in the startup OB:

// SCL in OB100 (startup)
CTRL_HSC( HSC    := 0,       // HSC instance
          CTRL   := 16#0,    // 0 = use configured default
          CV     := 0,       // initial count
          RV     := 0,       // reference value
          PERIOD := 0 );

// Reset in OB1 on operator request
IF "DB_Length".CmdReset OR "I_LengthReset" THEN
    CTRL_HSC( HSC  := 0,
              CTRL := 16#2, // 2 = write CV
              CV   := 0 );
END_IF;

Convert the HSC count to millimetres using the encoder pulses-per-revolution and the roller circumference:

// Constants
"DB_Length".ppr         := 4096;          // 1024-line encoder at 4x
"DB_Length".roll_dia_mm := 250.0;         // 250 mm roller
"DB_Length".pi          := 3.14159265;

"DB_Length".PulsesToMM := "DB_Length".ppr
                         / ("DB_Length".pi * "DB_Length".roll_dia_mm);

// Read count from HSC IDB
"DB_Length".Pulses       := "HSC_0".CountValue;
"DB_Length".Length_mm    := REAL_TO_LREAL("DB_Length".Pulses)
                            / "DB_Length".PulsesToMM;

7. Reading Drive Status, Errors, and Safety

7.1 Status word and fault code from PZD

ZSW1 (status word 1) and ZSW2 (status word 2) arrive in the first two PZD words of every telegram. Bit 3 of ZSW1 indicates an active fault; the actual fault number is in FAULT_CODE in telegram 3, 9, 102, 110, 390, and 391. Decode the fault number against the SINAMICS S110 List Manual to map the code to a message text. The top faults you will see on a band-pulling line are:

7.2 Reading the full fault buffer via acyclic services

For full fault text and timestamp, use acyclic parameter access. From TIA Portal, use the standard RDREC / WRREC instructions on the PROFIdrive slot. The fault buffer is parameter r0947[0..63] with r0949[0..63] as the time stamp. Read index 0 for the most recent fault:

// Acyclic read of r0947[0] (most recent fault number)
// Slot 0 = the drive's parameter channel
#ReqLen  := 4;
#WriteLen := 0;
"RDREC_DB".REQ        := "Cmd_ReadFault";
"RDREC_DB".ID         := 16#100;        // PROFINET/PROFIBUS HW ID of drive
"RDREC_DB".MLEN       := #ReqLen;
"RDREC_DB".INDEX      := 16#B02E;       // standard PROFIdrive parameter access
                                          // INDEX format 16#B0xx
"RDREC_DB".RECORD     := #FaultRecord;

IF "RDREC_DB".DONE THEN
    "DB_Status".LastFault := WORD_TO_INT("RDREC_DB".RECORD[0]);
    "DB_Status".FaultTime := DWORD_TO_UDINT("RDREC_DB".RECORD[2]);
END_IF;

7.3 Safety status

Two paths exist for safety on the S110:

1. STO via terminals on X131: STO-A and STO-B are 24 V inputs that pulse-inhibit the drive. Wire them to a dual-channel E-Stop relay. The safety state is reflected in ZSW1 bit 4 (OFF2 active) and the drive generates alarm A01600 / fault F01600 depending on configuration.
2. PROFIsafe over PROFIBUS or PROFINET: requires a CU305DP with a safety option card (e.g. CU305DP-2 PN with PROFIsafe profile 3.4). The S7-1200 supports PROFIsafe with the S7-1200F CPU (e.g. 1214FC). The safety state arrives in a separate F-host frame and in ZSW1 bit 6 (switch-on inhibit active when safe stop is engaged).

For most band-pulling lines, STO via terminals is sufficient. The S7-1200 reads the safety state from the drive over PROFIdrive (ZSW1 bits) and from the F-DI on the safety relay to compute its own safety feedback. Do not use a single-channel E-Stop in the safety path; the category is at minimum 1 (ISO 13849-1) for stationary pull lines.

8. Commissioning Step-by-Step

1. Wire and power up. Confirm Drive-CLiQ LEDs are steady green on the CU305DP and the SMC/SME module. Check that the 24 V control supply is clean (better than 21.6 V).
2. Run the S110 commissioning wizard in STARTER or Startdrive. Accept the topology, motor, encoder, and set the current limit to the nameplate value.
3. Save to ROM and run the drive in the local control panel of STARTER to verify the motor turns in both directions. Check the encoder direction with p1909 = 1 (only for motors with absolute encoder).
4. Set telegram 110 in the drive and match the same telegram in the S7-1200 device configuration.
5. Compile and download the PLC project. Go online with both the PLC and the S110.
6. Use the watch table in TIA Portal to monitor DB_Drive.ZSW1 and confirm the drive reaches the Ready to switch on and Ready to operate states before any setpoint is given.
7. Set STW1 to 0x047E (control word for OFF1 + pulse inhibit + PLC control + setpoint enable) and verify the drive returns no fault.
8. Configure the precondition: STW1 bit 0 (ON) is latched only when the position actual value is within the epsilon band OR the position controller is disabled. See ladder snippet below.
9. Enable the drive (STW1 = 0x047F) and apply a small JOG setpoint. Observe DB_Drive.G1_NIST_B ramping up to p2585.
10. Apply a 50 % override through p2646 via BICO and verify the speed scales correctly.
11. Reset the length counter from the HMI and verify G1_XIST_A returns to zero. Pull material and confirm the counter increments in proportion to the speed setpoint and the roller circumference.
12. Trigger a fault (e.g. disconnect a Drive-CLiQ cable) and confirm the PLC receives fault code, the HMI displays the message, and the operator can acknowledge and reset.
13. Test E-Stop: pull the STO input and verify the drive pulses-inhibit within 5 ms, the safety relay latches, and the HMI shows Safe Torque Off active.

8.1 Precondition ladder in SCL

// Latch ON command only when no fault and position is within epsilon
// (or position controller is disabled)
"DB_Drive".Precond_OK := (NOT "DB_Drive".FaultActive)
                          AND ("DB_Drive".PosControllerActive = FALSE
                                OR ABS("DB_Length".PosActual_LU) < 5);

IF "I_Start" AND "DB_Drive".Precond_OK THEN
    "DB_Drive".STW1 := "DB_Drive".STW1 OR 16#0001;   // bit 0 = ON
ELSE
    "DB_Drive".STW1 := "DB_Drive".STW1 AND 16#FFFE;  // clear ON
END_IF;

9. Verification Checklist

10. Troubleshooting Matrix

11. FAQ