PROFIBUS-DP operates as a master/slave system. It
usually consists of a single Master (usually integrated in the PLC) and up to 31
slaves per segment. When the Master is running, it simply polls each slave in
sequence. It is possible to have multiple masters on a network. The Masters then
share the network by passing a token. PROFIBUS-DP uses an industrially proven
physical layer based on RS-485. The system uses a
shielded twisted pair cable which is extremely resistant to electrical
interferences. PROFIBUS-DP accommodates a large number of I/O points which are
easily connected to the bus using
plug and play
cordsets and rugged industrial I/O stations.
With up to 126 addressable nodes, systems may have thousands of I/O points per
network. The Master receives the information it requires about a slave device
from a "GSD" file, which specifies all the necessary information including
communication rates, I/O data size, etc.. GSD files are available for all the
stations shown here. See bottom of page for a typical configuration.
Click HERE for more about Profibus from the Profibus website.