General Specification Electrical Function gmw3110 General Motors Local Area Network Enhanced Diagnostic Test Mode Specification

4.7 Communication Layer Interaction. 
The interaction between the communication layers in the tester and 
the ECU(s) are guided by the conventions discussed in OSI Service Conventions (ISO/TR 8509). Each layer 
provides a set of service primitives, which transports a certain type of parameters and data. The service 
specifications of ISO 11898 and OSEK-COM do not specify any implementation requirements but provide 
abstract service prototypes to support data exchange with the layers. 
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GM WORLDWIDE ENGINEERING STANDARDS 
GMW3110 
© Copyright 2010 General Motors All Rights Reserved 
February 2010 
Page 33 of 336 
4.7.1 GMLAN Communication Layer Interaction. 
Figures 3 and 4 shall illustrate how the communication 
layers for a GMLAN based system interact: 

Application Layer: GMLAN (e.g., GMW3110). 

Network Layer: OSEK-COM (USDT/UUDT Protocol). 

Data Link Layer: ISO 11898 (CAN). 

Physical Layer: GMW3122 (DW-CAN), GMW3089 (SW-CAN). 
Figure 3: OSI Layer Interaction Model 
A detailed description of the service primitives, and the data passed to each layer and retrieved from each 
layer (e.g., address information provided to/from the Network Layer) can be found in OSEK-COM (Network 
Layer) and ISO 11898 (CAN Data Link Layer). 
ISO 11898 provides service primitives for an unacknowledged data transfer (and unacknowledged remote data 
request) with up to 8 additional user data bytes. ISO 11898 only allows addressing via the CAN Identifier. 
OSEK-COM provides a set of service primitives for the transmission and reception of messages with up to 
4095 user data bytes. OSEK-COM provides a segmentation method for messages which do not fit into a single 
CAN frame as provided by ISO 11898 and, in addition, multiple addressing schemes (e.g., normal addressing: 
CAN Identifier; extended addressing: CAN Identifier, extended address = 1st data byte of CAN frame). OSEK-
COM uses the unacknowledged data transfer service primitives of ISO 11898 to transmit and receive CAN 
frames. 
GMLAN
APPLICATION LAYER
OSEK-COM
NETWORK LAYER
ISO 11898
DATA LINK LAYER
GMW 3122
DW-CAN
PHYSICAL
LAYER
GMW 3089
SW-CAN
PHYSICAL
LAYER
N_UUData.req
N_UUData.con
N_UUData.ind
L_Data.req
L_Data.con
L_Data.ind
OSEK-COM
service primitives
(UUDT/USDT protocol)
ISO 11898
service primitives
(Tx/Rx CAN frames)
N_USData.con
N_USData.ind
N_USData_FF.ind
N_USData.req
UUDT protocol
USDT protocol
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