What it means
A01921 is the message PROFIBUS: Receive setpoints after To
. The drive raises it because the output data of the PROFIBUS master — the setpoints — are received at the incorrect instant in time within the PROFIBUS clock cycle: they arrive after To, the moment at which the drive accepts the setpoints. As an alarm, the message triggers no automatic response from the drive. Depending on how the drive is configured, the same condition can also be issued as a fault; in that case the drive reacts with OFF1 (ramp-down of the motor to standstill) and the fault must be acknowledged immediately before the drive can be restarted.
Why it appears
- The output data of the PROFIBUS master (the setpoints) were received at the incorrect instant in time within the PROFIBUS clock cycle — after To, the time of setpoint acceptance.
What to check
- Check the bus configuration.
- Check the parameters for clock cycle synchronization and ensure To > Tdx — To is the time of setpoint acceptance, Tdx the data exchange time.
Acknowledging and restarting
The alarm itself requires no acknowledgement; eliminate the timing problem so that the setpoints are again received at the correct instant within the PROFIBUS clock cycle. If the drive is configured to raise the same condition as a fault, acknowledge the fault immediately — only then can the drive be restarted.
The same on every family
Every manual that describes A01921 gives it the same reaction, acknowledgement and message class.
| Drive family | Reaction | Acknowledge | Message class | Component | Manual |
|---|---|---|---|---|---|
| S120, S150 | NONE | NONE | Communication error to the higher-level control system (9) | None | SINAMICS S120, S150 List Manual · p. 2715 |
| G130, G150 | NONE | NONE | Communication error to the higher-level control system (9) | None | SINAMICS G130, G150 List Manual · p. 1491 |
The drives this code lives on
A01921 is described for G130, G150, S120, S150. These are the converters of those families in our catalogue — price on request.
Questions technicians ask
What does alarm A01921 on a SINAMICS drive mean?
It reports that the output data of the PROFIBUS master — the setpoints — were received at the incorrect instant in time within the PROFIBUS clock cycle, i.e. after To, the time of setpoint acceptance.
How do I fix A01921?
Check the bus configuration and check the parameters for clock cycle synchronization, making sure To > Tdx. To is the time of setpoint acceptance and Tdx is the data exchange time.
Does A01921 stop the drive?
As an alarm it triggers no automatic reaction, so the drive keeps running. If the same condition is configured as a fault, the drive reacts with OFF1 (ramp-down to standstill) and the fault must be acknowledged immediately before a restart.
What are To and Tdx in message A01921?
To is the time of setpoint acceptance and Tdx is the data exchange time. For the message to disappear, the clock cycle synchronization parameters must ensure To > Tdx.
Codes next to this one
Source
Written from Siemens' own List Manuals and operating instructions; every number, designation and parameter on this page is checked against them before publication.
All SINAMICS codes: fault and alarm codes · the A01xxx group · SINAMICS manuals · Siemens manuals