System Start-up Behaviour

Initial Operation

The PROFIBUS-DP protocol is automatically handled by the Communication Module and the operating system of the controller. The Communication Module is only active on the bus if it was correctly initialized before and if the user program is running. No connection elements are required for the cyclic exchange of process data via PROFIBUS DP. Special PROFIBUS DP functions can be realized using the function blocks of the corresponding PROFIBUS library.

Communication via PROFIBUS is established by the Communication Module when starting the user program and starts with the initialization of the configured slaves. After its successful initialization, the slave is added to the cyclic process data exchange. The “RDY” LED lights up steadily after at least one slave was successfully taken into operation. If the user program is stopped, the Communication Module shuts down the PROFIBUS system in a controlled manner.

The DP master operation mode is completely integrated to the operating system of the controller. The transmit or receive data of the slaves can be directly accessed in the corresponding operand areas. Access can be performed either via operands or symbolically. No function blocks are required.

The Function Block library contains various blocks which can be used e.g. to poll status information of the Communication Module or to execute specific acyclic PROFIBUS DP functions. If necessary, these blocks can be inserted additionally.

For further information on the configuration of PROFIBUS master/ PROFIBUS slave devices, see : PROFIBUS