At start-up, the PROFIBUS master sends a Set_Prm to each slave to parameterise it (User_Prm_Data), then a Chk_Cfg to verify the configuration of its modules, and finally Data_Exchange starts the normal cyclic I/O cycle.
True
The standard PROFIBUS DP slave start-up sequence is: (1) Slave_Diag for the initial diagnostic read, (2) Set_Prm to send parameters (watchdog time, prm data, etc.), (3) Chk_Cfg to verify that the modules actually present match the expected configuration, (4) Slave_Diag again to read diagnostics after parameterisation, and (5) Data_Exchange for normal cyclic I/O. Any problem during steps 1 to 4 keeps the slave in a "not operational" state and forces it into diagnostic mode.
If a slave never reaches Data_Exchange, capture the start-up sequence with ProfiTrace and find the first step that fails: that is where the misconfiguration sits, not later.
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