Higher Level Protocols - CAN System Engineering - page 208

○ SAE°J1979-DA, E/E diagnostic test modes (includes all standardized data
items: PIDs, TIDs, MIDs, ITIDs).
○ SAE°J2012-DA, diagnostic trouble codes (includes all standardized DTCs).
○ SAE°J1939, top level (includes all standardized SPNs and PGNs).
The session layer (OSI 5) services are defined in ISO 14229-2 Road vehicles—
Unified diagnostic services (UDSs)—Part 2: Session layer services. This standard
provides a protocol-independent standardized service primitive interface between
application layer services and transport protocol/network layer services. This stan-
dard is not limited to the standards as listed in Table 4.11 .
The transport protocol layer (OSI 4) and network layer (OSI 3) services are de-
fined in:
• ISO 15765-2 Road vehicles—DoCAN—Part 2: Transport protocol and network
layer services. This part of the standard is applicable to all three categories. The
legislated categories (OBD and WWH-OBD) have additional requirements de-
fined in ISO 15765-4, which are related to CAN identifier definition, transport
protocol timing, etc.
• SAE 1939-21, transport protocol is only applicable to WWH-OBD.
• SAE 1939-31, network layer is only applicable to WWH-OBD.
The data link layer (OSI 2) requirements are defined in:
• ISO 11898-1, Road vehicles—Controller area network (CAN)—Part 1: Data
link layer and physical signalling. This standard is applicable to all CAN net-
works independent of the upper OSI layer implementations.
• SAE 1939-21, Data link layer is only applicable to WWH-OBD.
The physical layer (OSI 1) requirements are defined in various parts of ISO 11898.
• Vehicle manufacturer-enhanced diagnostics can be implemented on any of the
following physical layer standards:
- ISO°11898-2, Road vehicles—Controller area network (CAN)—Part 2:
High-speed medium access unit (majority of automotive implementations).
- ISO°11898-3, Road vehicles—Controller area network (CAN)—Part 3: Low-
speed, fault-tolerant, medium-dependent interface.
- ISO°11898-4, Road vehicles—Controller area network (CAN)—Part 4:
Time-triggered communication.
• Legislated OBD is only allowed on ISO°11898-2, Road vehicles—Controller
area network (CAN)—Part 2: High-speed medium access unit.
• Legislated WWH-OBD is allowed on:
- ISO°11898-2, Road vehicles—Controller area network (CAN)—Part 2:
High-speed medium access unit.
- SAE J1939-15, Reduced Physical Layer, 250K bits/sec, Un-Shielded Twisted
Pair (UTP).
Figure 4.19 illustrates the most applicable application implementations utilizing the
DoCAN protocol.