Using SINA_POS and SINA_PARA in Parallel on S7-300 with CU310DP

Using SINA_POS and SINA_PARA in Parallel on S7-300 with SINAMICS CU310DP

1. Overview

The SIMATIC S7-300 controller family is widely deployed with the SINAMICS S120 drive line, where the CU310DP Control Unit provides the PROFIBUS (DP) interface. Two standard function blocks from the Siemens drive library — SINA_POS (FB 284) and SINA_PARA (formerly part of the DriveES / SIMOTION SCOUT libraries) — address fundamentally different communication patterns. SINA_POS is a cyclic positioner that operates over a configured Siemens standard telegram, while SINA_PARA issues acyclic parameter read/write jobs against the drive object.

Engineers regularly ask whether both blocks can be active simultaneously on the same axis, especially when an existing project already runs SINA_POS with telegram 111 and a new requirement demands torque and current readback. The short answer is yes — both blocks can coexist. The deeper question is which block (or which telegram extension) is appropriate for the new monitoring values, and the answer depends entirely on whether you need cyclic refresh or merely a snapshot.

2. Telegram 111 and SINA_POS Fundamentals

Telegram 111 is a Siemens standard telegram for the SINAMICS S120 / CU310DP. It is asymmetric and carries 12 words of process data in each direction (PZD-12/12). The default mapping for the closed-loop controlled drive is:

SINA_POS wraps the cyclic exchange and exposes a clean function-block interface (start, stop, mode, override, position setpoint, position actual, status bits). When you wire it in TIA Portal V13 or later, the block is connected to the telegram's hardware identifier (HWID) of the drive object — the same HWID that STARTER / Startdrive assigns to the configured telegram setpoint slot.

3. SINA_PARA Functional Model

SINA_PARA is an acyclic parameter access block. It triggers a DPV1 / acyclic record read or write on a parameter number, parameter index, and sub-index. Internally, on PROFIBUS, this is the Read Record / Write Record service; on PROFINET it is the equivalent PN IRT acyclic service. The block has a busy/done/error handshake:

• Set REQ := TRUE to start the job.
• The block writes the request into the acyclic buffer and clears DONE / ERROR.
• The CPU waits for the drive to respond; the round-trip time depends on bus load.
• When the reply arrives, DONE is set for one cycle (or latched depending on variant), and the data appears on the output buffer.
• If the drive rejects the request (invalid parameter, wrong access rights, faulty index), ERROR is asserted and a fault code is placed on FAULT_CODE.

Key parameter inputs of a typical SINA_PARA instance:

There is no continuous stream of data — one REQ edge produces one DONE with one new value. To re-read the same value you must retrigger REQ.

4. Why SINA_PARA is Suboptimal for Continuous Torque / Current Monitoring

Acyclic communication is designed for configuration, commissioning, diagnostics, and infrequent parameter access — not for closed-loop control or HMI live values refreshed at the bus cycle rate. On a PROFIBUS DP network with a CU310DP, the following limitations apply:

• Round-trip time. A single acyclic request typically takes 1–3 bus cycles plus CPU processing, often 20–100 ms or more depending on DP baud rate (1.5 Mbit/s, 12 Mbit/s) and bus load. Under heavy cyclic load, the acyclic channel can be deferred.
• No time-deterministic refresh. If you retrigger every 100 ms but the previous job has not finished, the second request is queued or rejected depending on the block variant. You must wait for DONE or ERROR before issuing the next job.
• Single parameter per request. To read both torque and current you must sequence two jobs, doubling the effective latency and doubling the bus load.
• No "always-fresh" value. An HMI screen polling a tag connected to the last acyclic result will see the same value held until the next job completes, which is misleading.

5. Extending Telegram 111 with Free PZD (Recommended Path)

The correct approach for reading additional SINAMICS parameters on a CU310DP is to extend the standard telegram 111 with supplementary free PZD slots. The free PZD extension uses a sub-slot — in TIA Portal you add the "Supplementary data" or "Free telegram configuration" item to the drive device and assign SINAMICS parameters (PZD) to the additional words.

To expose torque and current over the cyclic channel:

1. In Startdrive / SCOUT, open the drive's Communication → Telegram configuration and keep telegram 111 selected.
2. Add a Free PZD block in the drive direction. Each block consumes 1, 2, 3, 4, 5, 6, 7, or 8 PZD words as you configure.
3. Assign the following SINAMICS parameters to the new PZD slots:

4. Compile and download the drive configuration. The drive will broadcast the extended telegram.
5. In TIA Portal, re-insert the drive device (or refresh the topology) so the new PZD slots appear in the I/O view.
6. Either wire SINA_POS to the original 12/12 PZD words only and use DPRD_DAT / DPWR_DAT to access the additional words, or upgrade to the variant of SINA_POS from a later library that exposes a UserData interface.

Because the extension lives in a sub-slot of the same module, the cyclic bus cycle is unchanged. Torque and current become available at the configured PROFIBUS cycle (typically 2–8 ms on CU310DP) and SINA_POS continues to function on its original 12 words.

6. HWID: Module Access Point vs Telegram Setpoint

This is the most common source of integration errors. A SINAMICS drive object on PROFINET or PROFIBUS exposes two distinct HW identifiers in TIA Portal:

• Module Access Point HWID — the diagnostic / acyclic access path. Used by SINA_PARA and by acyclic blocks such as RDREC / WRREC.
• Telegram Sub-slot HWID(s) — the cyclic I/O data slots. The first sub-slot is the "setpoint / actual value" word, and any free PZD extensions are additional sub-slots with their own HWIDs.

Wiring rules:

• SINA_POS → must be wired to the cyclic sub-slot HWID, not the module access point.
• SINA_PARA → should be wired to the module access point HWID, which is robust against subsequent free PZD changes.
• DPRD_DAT / DPWR_DAT for the extension → wired to the corresponding sub-slot HWIDs of the free PZD.

7. PROFIBUS DP vs PROFINET Considerations for CU310DP

The CU310DP variant is a PROFIBUS-DP slave. Several of the published Siemens application examples for SINA_POS and SINA_PARA are written for the CU310PN (PROFINET) variant. The differences that matter when porting an example from PN to DP:

The block code in TIA Portal is identical; only the device selection and HWID resolution differ. Engineering the project from a PN example on a DP hardware will compile cleanly but the acyclic jobs will time out until the HWID is corrected to the slot 0 access point.

8. Step-by-Step Implementation

Prerequisites

• TIA Portal V13 SP1 or later with Startdrive (or SCOUT for older projects).
• S7-300 CPU with PROFIBUS master interface (e.g. CPU 315-2 DP / 317-2 DP / 319F-3 PN/DP).
• SINAMICS S120 with CU310DP Control Unit, firmware ≥ V4.5 recommended for stable free PZD.
• Drive library containing SINA_POS (FB 284) and SINA_PARA — typically delivered with Startdrive or the DriveES blocks.

Procedure

1. Keep the existing telegram 111 configuration. The currently running SINA_POS instance must not be disturbed — no recompile of its HWID, no change to its process data length.
2. Add free PZD to the drive. In the drive's Device view in TIA Portal, select the SINAMICS drive. Under Properties → Telegram configuration, the active telegram 111 is listed. Add a free PZD sub-slot. Configure two or more words and assign them to r0027 and r0031 (or any other SINAMICS parameters you want).
3. Compile and download the drive project. Use Startdrive to load the new free PZD configuration into the CU310DP. The drive performs a brief initialization; the cyclic communication resumes within seconds.
4. Refresh the TIA Portal device proxy. Reopen the device view of the S7-300 station. The free PZD appears as an additional sub-slot under the drive with its own HWID. Note the HWID — it will look like 256..271 in the HW identifier list.
5. Wire the new free PZD to a data block. Use a global DB to receive the values. The simplest is to drop DPRD_DAT (SFC 14) in OB1 and read the new HWID into a structure:

// STL or SCL equivalent in OB1 (S7-300/400 style)
CALL  "DPRD_DAT"
      LADDR  := 264          // free PZD sub-slot HWID
      RET_VAL:= MW 200
      RECORD := P#DB10.DBX0.0 BYTE 8   // 2 words = 4 bytes; use 4 bytes for two INT
      NOP   0;

6. Add SINA_PARA in parallel. Drop a new instance of SINA_PARA in the same cyclic OB. Wire its HWID to the module access point of the CU310DP (not the free PZD). Trigger a low-priority job from a cyclic timer OB (e.g. OB35) to read non-critical parameters such as the drive's serial number, fault memory, or runtime counter. Do not retrigger the same parameter every 100 ms; wait for DONE or ERROR.
7. Leave SINA_POS untouched. The original SINA_POS instance continues to operate on its 12/12 PZD words with the original HWID. No change required.
8. Verify cyclic update rate. In online mode, force-change the value of r0027 from Startdrive and confirm that the corresponding word in DB10 changes within one DP cycle of the OB1 scan.

9. Reading Torque and Current on HMI

Once the free PZD is read into the DB, the HMI (WinCC Professional / WinCC flexible / TIA Panel) only needs to display the tag. No further code is required. Suggested scaling on the HMI side:

10. Verification and Diagnostics

After commissioning, the following checks should pass:

• Online → Telegram length. In Startdrive, the active telegram shows telegram 111 with N free PZD words. Match the configured length against the I/O length visible in the S7 hardware diagnostic buffer.
• SINA_POS status. Status word bit pattern matches the drive's actual operating state. Position actual updates each OB1 cycle.
• Free PZD readback. DB10 values change in real time when the load on the drive changes (apply a torque disturbance and observe the r0031 word increase).
• SINA_PARA handshake. The acyclic job completes with DONE = TRUE and a non-zero FAULT_CODE = 0 only on intentional fault tests.
• CPU diagnostic buffer. No I/O faults, no access errors. A persistent DP slave diagnostic indicates an HWID mismatch.

11. Troubleshooting Matrix

12. Field Notes and Library Variants

Different versions of the SINA_POS / SINA_PARA library exist:

• DriveES SIMATIC V5.x / V6.x — the original S7-300/400 incarnation. Uses FB 284 for SINA_POS and FB 285 for SINA_PARA. Slightly different instance interface compared to TIA Portal versions.
• TIA Portal V13 SP1 library — blocks ported to SCL, identical behaviour, modern TIA DB-aware interfaces.
• Startdrive V14 SP1 and later — SINA_POS exists in multiple variants (SINA_POS, SINA_POS_TLG111, SINA_SPEED, SINA_PARA) inside the Startdrive toolbox.

When porting a DriveES V5 project to TIA Portal, the block instances can be replaced one-for-one because the I/O pin names are preserved. The HWID is the only thing that requires re-resolving through the new device proxy.

13. FAQ