Baumer GNAMG - Manual (Page 7)

Manual_GNAMG_Profibus_EN.doc 7/19 Baumer IVO GmbH & Co. KG
04.05.11 Villingen-Schwenningen, Germany
5. Data exchange between Profibus-DP devices
5.1. Telegram structure
The diagram shows the telegram structure.
Telegram structure
DP Master
Request telegram
DP Slave
Footer info Output data Header info
Response telegram
Header info Input data Footer info
5.2. Initialization, restarting and user data communication
Prior to user data exchange between master und slave every slave is re-initialized. The master transmits
parameterization and configuration data to the slave. Only when parameterization and configuration data
are congruent to the data stored in the slave the user data exchange is proceeded in the following way:
Diagnostic request from master
The master transmits a Slave Diagnosis Request (Slave_Diag), the Slave replies by a Slave Diagnosis
Response.
The master utilizes this data to check whether the slave exists in the bus and is ready for parameterization
and configuration.
Slave parameterization
The master transmits a Slave Parameter Request (Set_Prm).
By the parameterization data the slave receives information about current bus parameters, monitoring
times and slave-specific parameters. During the project processing phase the parameters are partially
adopted directly or indirectly from the GSD file. The slave compares this parameterization with its own
stored data.
Slave configuration
The master transmits a Check Configuration Request (Chk_Cfg).
The master informs the slave of amount (number of data bytes) and structure (data consistency) of the
input and output ranges to be exchanged. The slave compares this configuration with its own
configuration.
Diagnosis request prior to data exchange
The master transmits another Slave Diagnosis Request (Slave_Diag), the slave replies by a Slave
Diagnosis Response.
Now the master is checking whether parameterization and configuration are congruent with the data
stored in the slave. If the data requested by the master are admissible and no error has occurred, the
slave is signalising its readiness for user data transfer by help of the diagnosis data.
Data_Exchange
The slave will only respond to the master it was parameterized and configured by.
The master transmits a user data request (Data_Exchange), the slave replies by a user data response
informing the master whether current diagnostic results are available. The slave will not transmit the true
diagnostic and status information until a diagnostic telegram by the master is received.