Baumer G1-G2-G0-GE-GB-GXxxx - Manual (Page 9)

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6. Data exchange between Profibus-DP devices
6.1. Telegram structure
The diagram illustrates the telegram structure.
Telegram structure
DP Master
Triggering telegram
DP Slave
Footer info Output data Header info
Reply telegram
Header info Input data Footer info
6.2. Initialization, restarting and user data communication
Before an exchange of useful information between the master and slave, every slave is re-initialized. The
master transmits parameterization and configuration data to the slave. Only when the parameterization and
configuration data is in agreement with the data stored in the slave can user data be exchanged. This takes
place in the following way:
Diagnostic request from the master
The master transmits a Diagnosis Request to a slave (Slave_Diag), and the slave responds with a Slave
Diagnosis Response.
The master uses this data to check whether the slave exists in the bus and is ready for parameterization and
configuration.
Parameterization of the slave
The master transmits a Parameter Request to the slave (Set_Prm).
The Slave receives information about the current bus parameters, surveillance times and slave-specific
parameters via the parameterization data. The parameters are taken over during the project processing
phase partially directly or indirectly from the GSD file. The slave compares this parameterization data with its
own stored data.
Configuration of the slave
The master transmits a Check Configuration Request (Chk_Cfg).
The master informs the slave of the scope (number of data bytes) and the 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 answers with a Slave
Diagnosis Response.
The master now checks whether the parameterization and configuration agree with the data stored in the
slave. If the data requested by the master is admissible and if no error exists, the slave signals its readiness
for the transfer of user data by means of the diagnosis data.
Data_Exchange
The slave now responds exclusively to the master which has parameterized and configured it.
The master transmits a user data request (Data_Exchange), the slave answers with a user data response. In
this response, the slave informs the master whether current diagnosis results are available. The slave only
makes known the actual diagnosis and status information after the master's diagnosis telegram.