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

Figure 16: ECU P2
CE
 Timing Parameter Definition - Single Frame Response Message 
Figure 17: ECU P2
C
 Timing Parameter Definition - Multiple Frame Response Message 
Request
USDT-SF
100
P2
CE
0
ECU Transmit
Tester Transmit
ECU NWL
Tester NWL
req
con
ind
req
con
ind
Request
USDT-FF
. . .
Tester Transmit
ECU Transmit
USDT-FC
USDT-CF
USDT-CF
100
P2
CE
0
USDT-FC
Tester NWL
ECU NWL
req
con
ind
req
ind
con
ind
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GM WORLDWIDE ENGINEERING STANDARDS 
GMW3110 
© Copyright 2010 General Motors All Rights Reserved 
February 2010 
Page 51 of 336 
Figure 18: ECU P2
C
 Timing Parameter Definition - UUDT Response Message(s) 
Note:
Figure 18 describes the timing parameter P2
CE 
for services which send UUDT responses. Refer to 
diagnostic services $AA and $A9 for timing requirements (P
X
) of UUDT responses following the initial UUDT 
response (if applicable). 
The transmission and reception of USDT messages (single and multi-frame messages) is completely handled 
in the network layer. 
When the application layer transmits a message, it sends a transmit request (N_USData.req) to the network 
layer and provides the data to be transmitted. The network layer performs the necessary timing handling to 
make sure that the data is transmitted (segmented data transfer, if data length requires multi-frames). The 
network layer indicates when the single frame or multi-frame message is completely transmitted 
(N_USData.con) or when an error occurred during the transmission (N_USData.ind with negative result code). 
When receiving a multi-frame message, the application layer gets an indication from the network layer that a 
multi-frame message has started (N_USData_FF.ind) and gets another indication when the USDT multi-frame 
message is completely received (N_USData.ind) or when an error occurred (N_USData.ind with negative 
result code). Single frame messages are indicated to the application layer after its completion via a single 
indication (N_USData.ind with length 
≤ 7 for normal addressing and length ≤ 6 for extended addressing). 
The segmentation of data into multiple single frame UUDT response messages (diagnostic services $AA and 
$A9) is completely handled by the diagnostic application. The diagnostic application builds the individual UUDT 
messages and provides them to the network layer for transmission on the link (N_UUData.req). The network 
layer indicates when each individual UUDT message is completely transmitted (N_UUData.con).