-
16
-
4.6 DP master class 1 and class 2
The class 1 master refers to the controller that performs cyclic I/O data exchange with the slaves, while a
class 2 master is a B&B device that generally only reads the slaves IO data in a read-only manner.
PROFIBUS-DP-V1 essentially refers to the acyclic read and write telegrams used to acyclic access data
records in the slave. With DP-V1 as well, a distinction is made between class 1 and a class 2 master. The
acyclic class 1 (C1) or class 2 (C2) connection differ in that the acyclic C1 connection is established with the
DP startup of the cyclic DP operation. From the state WAIT-CFG of the slave, acyclic DP-V1-C1 read and
write telegrams can be sent from the master to the slave, while the C2 connection has a separate connection
independent of the cyclic DP connection, which is usually is performed by a second (C2) master, so that e.g.
a manufacturer-specific configuration and diagnostics tool can access the data of the slave. When using two
masters, however, it must always be remembered that they share the bus access (a token is exchanged), so
that the time relationships are less favorable than with a mono-master system
.
