Scenarios

Basic explanatory notes regarding the Low Level scenarios:

The initialization step begins with the configuration of the TCP/IP interface, during which the IP address and the communication port are set. Then, various protocol parameters and parameters of the send and receive buffers are set. This is followed by establishment of the TCP/IP connection with the aid of function blocks from the TCP/IP function.

Data are then received and loaded from the receive buffer with the action fbBuffer.RxRemoveObj until the buffer is empty. The received data are sorted by type ID and object address. After sorting, the respective data are stored in a variable with the function F_iecCopyStreamToBuffer and then split according to the components set out in the standard. If the command for a general interrogation or the interrogation command for a specific group of interrogations is received in the slave, the corresponding transfer procedure for interrogation commands is triggered immediately, and the data points defined for the respective group are written to the send buffer. Sending of data is described in more detail in the following paragraph.

Both in the master and in the slave this is followed by sending of the data to be transferred outside of or in addition to an interrogation group. First, common transfer details of the data points such as ASDU address, number of objects to be transferred, reason for the data transfer and priority class are written to the structure stTxAsdu.ident. Then the protocol frames of each data point, consisting of type ID, object address and object-specific data, are written to the structure stTxAsdu. This is followed by copying via the function F_iecCopyBufferToStream and writing to the send buffer via the action fbBuffer.TxAddObj. Finally, any errors are read from the error memory and listed in an error output.

The process of reading, writing and subsequent error handling is repeated cyclically.