Hello everyone,

I am currently commissioning a servo drive using the SINAMICS Control Unit CU320-2 DP (6SL3040-1MA00-0Axx, Firmware V5.2.3) via PROFIBUS. The connection through SINA_POS is working correctly — the drive is under control, and basic communication is established.

However, I am facing issues with reading drive and motor parameters using the Free Telegram interface.

I have added the Free Telegram configuration and assigned it to parameters I want to monitor — for example, motor temperature (r0035). The PLC is receiving data from the drive, but the values do not make sense and appear unformatted.

🔹 My questions are:

1. How can I decode the data received from the drive via Free Telegram? I assume the temperature value is a REAL (IEEE 754) type, but I may need to swap bytes or words — can someone confirm the correct method to decode this?
2. Could you please help me understand the data structure used in the Free Telegrams both from drive to PLC and PLC to drive (e.g., how 32-bit values like REAL or DINT are transferred using 2 words)?
3. Regarding the Free Telegram:
   • I understand that the PZD Send and PZD Receive can be up to 8 Words (16 bytes) each. Is this correct?
   • If I need to transfer more parameters (e.g., temperature, torque, speed, status words), what is the recommended way to structure the telegram or extend data exchange?

Thank you in advance for any help or documentation references you can share. I'm trying to properly monitor motor status and send control values via Free Telegram but struggling with the data format and interpretation.

Best regards,
Ami
(PLC programmer / commissioning engineer)