wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

LIN-Bus 45-3
System design
tool
Cluster design
LIN description
file (LDF)
System
generator
Master
Slave 1
LIN
LIN analyzer/
emulator
Node capability
files (NCF)
Slave 2
Off-the-shelf
slave node
Cluster
Debugging
FIGURE 45.2
Workflow with off-the-shelf slave nodes.
45.3 Communication Concept
LIN uses the master–slave principle for the medium access control feature. This principle allows master
and slave nodes to be implemented with minimal hardware resources. The master node is usually implemented
in a control unit or in a gateway that possesses the necessary resources.
The specification also defines a master task and a slave task. The master task initiates every communication.
A message will always consist of a header generated by the master task and a response from
the slave task. As the master node should also be able to send messages to the slave nodes, along with
the master task a slave task can also be integrated into the master node (see Figure 45.3) [Grz05]. This
provides the possibility of integrating several slave tasks onto a hardware platform.
The LIN communication scheme is based on the producer–consumer model. Therefore, the specification
denotes the transmitter as the “publisher” of the message and the receiver(s) as “subscriber(s).” LIN,
like CAN, uses identifiers to uniquely identify a message. As well as a point-to-point communication
scheme, multicast and broadcast communication schemes are also supported. Figure 45.4 shows the
three possible communication relationships:
a. A slave module responds to a master request
b. The master sends a message to one or more slave nodes
c. The master initiates the communication between two slave nodes
45.4 Physical Layer
It was a goal of the LIN design to achieve a simplistic wiring topology. The simple single-wire bus
connects to each node in the cluster and switches from ground to battery-level voltage.
The physical layer is based on the ISO 9141 standard [ISO9141]. It consists of the bidirectional singlewire
bus line (LIN) that is connected via a pull-up resistor (R) and a diode to the internal supply voltage
(V SUP ) via a transistor (component of the transceiver) to the ground (GND) (see Figure 45.5a). The diode
© 2011 by Taylor and Francis Group, LLC