Introduction and Overview
1/4
WL Circuit Breaker
• Pure master-slave system
• Pure master-slave system with
token passing
• A system combining both
procedures
Graphic 1-4 shows an example with
3 master modules and 7 slaves. The
3 master devices form a logical ring.
The MAC (medium access control)
monitors the token. It creates the
token in the ramp-up phase and
monitors whether just one token
is really circulating in the ring.
Each slave that communicates
cyclically via the PROFIBUS-DP is
assigned a class 1 master. Cyclic
data exchange is carried out to
the standard DP profile (DPV0).
A class 1 master is mainly used for
automation tasks. In addition to
cyclic data exchange, a class 1
master can also establish an acyclic
communication connection to its
slaves, which enables it to use the
extended slave functionality.
A class 2 master is particularly
suitable for commissioning,
diagnosis, and visualization tasks.
In addition to the class 1 master,
it is connected to the PROFIBUS-DP
and can access slaves and exchange
data using acyclic services
(providing the slaves allow this).
Acyclic data transmission is carried
out via DPV1. The existing PROFIBUS
standard has been extended to
include DPV1 with a number of
additional functions. This enables
the slave to be reparameterized
during operation, for example,
an acyclic data transmission to be
carried out. DPV1 also allows data
to be read directly from the slave
by a class 2 master, even though
this is still logically connected to a
class 1 master. Both DPV1 and DP
standard transmission takes place
across one line.
Acyclic data transmission can be
used when an operator control and
monitoring system, such as WinCC,
is implemented. The PC used with
an integrated PROFIBUS-DP interface
card then takes on the role of the
class 2 master, from which the data
records are transmitted via DPV1
and new values set, for example,
if the tripping current value is
changed. Cyclic data exchange
between the circuit breaker and
the PLC continues as normal.
WL PROFIBUS Communication and Electronic Accessories • July 2004
