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PROFIdrive drives, such as Siemens SINAMICS, are controlled with a 16-bit control word (STW1) and report back with a 16-bit status word (ZSW1). With standard telegram 1, the PLC sends STW1 plus a speed setpoint and receives ZSW1 plus the actual speed.

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Why 047E and then 047F

A PROFIdrive drive follows a state machine. It only starts when it sees ON (bit 0) rise from 0 to 1 while OFF2, OFF3 and the enable bits are already set:
  1. Send 16#047E. Bits 1–6 and bit 10 are set and ON is 0, so the drive goes to Ready to switch on.
  2. Send 16#047F. Bit 0 goes to 1, and the drive switches on and runs at the speed setpoint.
If the drive has a fault, set bit 7 (Acknowledge fault, for example 16#04FE) and then go back to 16#047E. If you send 16#047F straight after power-up, many drives stay in Switching on inhibited because they never saw ON go from 0 to 1.

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Speed setpoint scaling

The speed setpoint in telegram 1 is a signed 16-bit value where 16#4000 (16384) means 100 % of the reference speed. On SINAMICS drives the reference speed is parameter p2000. Negative values turn the motor the other way.
Bits 0–7 and 10 of STW1, and bits 0–10 of ZSW1, are defined by the PROFIdrive profile. The remaining bits are manufacturer-specific. The SINAMICS meanings shown in the tool are the common defaults, so always check your drive’s manual and the telegram you configured.

Bit and number converter

Toggle bits and convert between decimal, hex, binary and BCD.

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