16
◊
Received status byte; 1 byte.
◊
Message bytes ...
5.1.4.2 Received message example
As an example the byte sequence $A7 $B6 $C5 plus CRC or checksum byte appears on the
network. The message is received by the AVT-718 and the following byte sequence is passed to
the host computer: $04 $00 $A7 $B6 $C5 (time stamping is disabled).
The byte $04 indicates that it is a received message and that four bytes follow.
The byte $00 is the received message status byte and indicates that no errors were found.
(Received message status byte, bit definitions are listed in the next section.)
The message bytes then follow. Note that the CRC or checksum byte is stripped off.
5.1.5 Received Message Status Byte Definitions
The user should consult the “Master Commands and Responses” guide for the most up-to-date
listing of the bit definitions for the received message status byte for each mode of operation.
5.1.6 More Examples
To illustrate the construction and decoding of packets between the control computer and the
AVT-718 Multiple Interface, several examples are provided.
Example #1: Want to request the current operational mode.
Command:
D0
.
The AVT-718 responds with:
91 14
.
The ‘
9
’ indicates a board status response.
The ‘
1
’ indicates one byte follows
The ‘
14
’ indicates UBP mode.
Example #2: want to send a message out on the bus.
Command:
04 32 89 AC 5F
.
The AVT-718 responds with:
01 40
.
The ‘
0
’ indicates a received message from the network.
The ‘
1
’ indicates only one byte follows. The one byte is the received message status byte.
The ‘
40
’ is the received message status byte with bit
6
only being set.
Bit
6
is set. This means the received message was ‘from this device’ meaning the AVT-718
unit.
Messages transmitted by the AVT-718 are received by the AVT-718.
They are checked for errors.
Unless otherwise configured, only the status byte is sent to the host
In UBP mode, the AVT-718 will also send the transmission acknowledgment
A1 20
which
indicates that the message was successfully transmitted.
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