PLX51-PBM
PROFIBUS DP
PROFIBUS DPV0/DPV1 Master or Slave to EtherNet/IP™ or Modbus® Gateway
User Manual
ProSoft Technology, Inc.
Page 191 of 196
10.5
Acyclic Communication
In addition to the cyclic data exchange, the PROFIBUS protocol has the option of
acyclic communication. This service is not configured. There are 2 different
communication channels possible between the requested master and the slave:
MS1 channel
(MS1 connection): can only be established if cyclic data exchange
is taking place between that master (DPM1) and the slave
MS2 channel
(MS2 connection): is possible with several masters simultaneously,
but the connection must be established explicitly by the master.
Acyclic reading and writing of data requires an established MS1 or MS2 connection.
For the MS1 channel, 3 conditions must be satisfied:
The slave device must support the MS1 channel (key
C1_Read_Write_supp
at 1
in the GSD file)
The DPV1_enable bit must be set during the parameter assignment
Data exchange is taking place
For the MS2 channel, the connection must be explicitly initiated by the master. The
maximum number of possible MS2 connections to the slave must not be reached.
The connection can be closed by either the master or the slave device.
10.6
Topology of PROFIBUS DP
PROFIBUS devices are connected in a bus structure. Up to 32 stations (master or
slaves) can be connected in one segment. The bus is terminated by an active bus
terminator at the beginning and end of each segment. Both bus terminations must
always be powered. When more than 32 stations are used, repeaters (line amplifiers)
must be used to connect the individual bus segments.
