Checksum; Id Byte Only Message; Communications Example - AVT 84 Series Manual

As of firmware version 1.1 the new "5x 28" command can be used to enable or disable LIN message
processing using the ID byte. The default condition is enabled.
When ID byte processing is enabled the ID byte is used to determined expected message length.
When ID byte processing is disabled, maximum frame time is used to determine the end of a LIN
message frame. Maximum frame time, in milliseconds, can be set using the "5x 52" command.

8.2.2 Checksum

Both "Classic" and "Enhanced" checksum methods are available through the 5x 5A command.

8.2.3 ID Byte Only Message

If the Master on a LIN bus transmits the ID byte and no module on the bus responds, then the message
is an "ID byte only" message. In firmware versions 1.0 through 1.4, if the AVT-84x interface received
an ID byte only message, an error packet was sent to the host and the ID byte only message was
discarded.
There was no way to "see" the ID byte and no way to suppress those error packets.
In firmware version 1.5 and later, the "5x 66" command and function were implemented.
The "52 66 00" command is the default condition. Operation is: ID byte only messages are discarded
and nothing is sent to the host.
The "52 66 01" command causes the AVT-84x to notify the host that an ID byte only message was
received and report the ID byte. The format of the notification is (time stamps disabled):
03 05 03 xx
or 03 05 83 xx
03
05
03 or 83
xx

8.2.4 Communications Example

This example is to enter CAN mode, receive a message from the LIN network (passively) and to send
messages to the LIN network in the three possible methods. Time stamps are disabled.
; enter CAN mode
E1 99
; receive a LIN network message (passively)
05 05 00 C4 78 9A
; 0 indicates "from" the network
; 5 count of bytes to follow
; 05 channel 5 - LIN
; 00 status byte, no bits set indicates no errors detected
; C4 message ID
; 78 9A message data field
AVT-84x Multiple Interface
means from the network, 3 bytes follow
channel 5 = LIN
receive status byte, frame timeout bit may or may not be set
message too short and checksum error bits are set
the received ID byte
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