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

LIN-Bus 45-11
The successful_transfer status is set when a frame has been successfully transferred by the slave, that
is, a frame has either been received or transmitted.
45.7 transport Layer Protocol
The LIN transport layer provides a data transfer between master and slave node for diagnostic, slave node
configuration, and identification purposes. It achieves segmentation/desegmentation and flow control. The
diagnostics message transfer is compatible with CAN-based diagnostic protocols. Typically diagnostics
are performed from a tester where a LIN master can pass the received tester requests to the relevant LIN
slaves. A LIN slave receives requests, routes them to the appropriate service, and constructs the response.
LIN version 2.0 defines a transport layer protocol that was deduced from the ISO 15765-2 protocol
[ISO15765-2]. It tunnels Keyword Protocol 2000 (KWP-2000) and Unified Diagnostic Services (UDS),
as defined in ISO 15765-2 and ISO 14229-1 [ISO14229-1], and provides the configuration and diagnostic
service for LIN slaves. Therefore, the full transport layer specification does not have to be implemented
in all slave nodes; LIN version 2.1 specifies three diagnostic classes as:
Class 1 supports single frame transport protocol only, with fault indication by signals.
Class 2 provides node identification support, implementing the multi-frame transport protocol,
but supporting only the UDS/KWP-2000 “read by identifier” service.
Class 3 slave nodes are the most complex nodes. They execute additional tasks beyond the basic
sensor and support the services: diagnostic session control, input/output control, read/clear
diagnostic trouble code information, as well as optional flash programming features.
The transport layer protocol uses two diagnostic frames: the MRF and the SRF. The MRF (ID = 0x3C)
is the diagnostic request, where the master transmits both the frame header and the frame response to
a slave node. The SRF (ID = 0x3D) represents the diagnostic response, where the master transmits the
header, and a slave transmits the response to the master that contains the answer of the preceding MRF.
The protocol uses single frames (SF), but for multi-frame support, first frames (FF) and consecutive
frames (CF) are mapped into the eight data bytes of a LIN frame. A MRF is always transmitted to all
slave nodes (broadcast traffic). Therefore, the slave node address, the so-called node address for diagnostics
(NAD) is stored in the first data byte. The second data byte stores the protocol control information
(PCI) of the transport layer and the third data byte stores the service identifier (SID) defined in the
standards ISO 15765-3 (KWP-2000) [ISO15765-3] and ISO 14229-1 (UDS) [ISO14229-1].
A simple example for use of a single frame transport protocol is the node configuration service
“assign NAD” (see Figure 45.10). With this service, the slave nodes in a cluster can assign a unique NAD.
Master
Slave
ID = 0×3C
Initial
NAD
PCI
0×06
SID
0×B0
D1
Supplier ID
LSB
D2
Supplier ID
MSB
D3
Function ID
LSB
D4
Function ID
MSB
D5
new NAD
MRF
assign NAD
request
ID = 0×3D
Initial
NAD
PCI
0×01
RSID
0×F0
D1
0×FF
D2
0×FF
D3
0×FF
D4
0×FF
D5
0×FF
SRF
positive
assign NAD
response
FIGURE 45.10
The “assign NAD” service as an example for a single frame.
© 2011 by Taylor and Francis Group, LLC