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5.3.3 PWM “Look Alike”
There exists a “Look Alike” mode for PWM operations. This mode was developed to allow the
AVT-718 to ‘mimic’ VPW operations while in PWM mode.
More specifically, an OBD-II query in VPW mode is of the form: 68 6A F1 xx yy
But in PWM mode the same query is of the form: 48 6A xx yy. Note that the priority/type byte
is different and the source address byte is missing. The response from the AVT-718 in normal
PWM mode includes the CRC byte at the end.
If the AVT-718 is put into PWM mode and “Look Alike” is enabled the user can treat the AVT-
718 as if it were in VPW mode (for OBD-II queries). The AVT-718 will change the “68” byte
from the host to “48”, the source address byte is stripped out and used to update the HBCC node
address, and the CRC byte is stripped from the response message.
Note that the received CRC byte is stripped from the received message when either the CRC byte
forwarding is disabled (5x 01 command) or when “Look Alike” mode is enabled
(5x 14 command). The user should be aware of the interaction between these two commands.
5.4 KWP Mode
Consult the latest version of the “Master Commands and Responses” document for detailed
information on the commands supported by the AVT-718 while in KWP mode of operation.
The latest version of the “Master Commands and Responses” document can be obtained from our
web site at:
http://www.avt-hq.com
Note: Since the AVT-718 supports operations in Keyword Protocol 2000 mode, it will
support ISO 9141 and ISO 9141-2 operations.
Operations in KWP mode are slightly different than in VPW mode.
When first entering KWP mode, the AVT-718 is disconnected from the network (K-line). There
are two ways to connect to the network.
1. Conduct a communications initialization with the vehicle. The AVT-718 supports all three
methods, as required by the ISO 14230 specification. The three initialization methods are
mentioned here. Consult the document “Keyword Protocol 2000 Initialization” for detailed
information about each of these initialization sequences.
A. CARB mode initialization. This is the mode that should be used for ISO 9141-2
applications; such as OBD-II operations. The command is: $61 11.
B. 5-Baud mode initialization. The command is: $61 12.
C. Fast initialization. The command is: $6x 13 yy zz ...
Note that following successful initialization of the communications link, the AVT-718
will monitor for transmitted messages. If no transmit activity is sensed within 4.5
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