User Guide

12 HDV100A3 Command & Response Manual-1306cr
B&B Electronics -- 707 Dayton Rd. -- PO Box 1040 -- Ottawa, IL 61350
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J1708 Commands
Receiving Data from the J1708 Bus
After the HDV100A3 is set into its Intelligent mode of operation
and the RS-232 data rate is configured, you are now ready to communicate
with the J1708 bus. A receive command must be sent to the HDV100A3
before attempting to transmit to the bus. The receive message synchronizes
the HDV100A3 with the bus. To start receiving J1708 bus data, send the
following to the HDV100A3.
Byte
Number
Byte Value
(hex)
Byte Function
1 01 Start of frame
2 02 The number of control bytes
3 01 ID byte 01= J1708
4 11 Function code 11 hex start receive
5 00 Number of data bytes (00 place holder)
6 15 Checksum (bytes 1 through 5 added together)
After sending this command to the device, the device will respond
with a confirmation message. The message confirms that the command was
received by the HDV100A3 and the checksum verified correctly. The reply
from the device is formatted as follows:
Byte
Number
Byte Value
(hex)
Byte Function
1 01 Start of frame byte
2 01 Control byte
3 01 ID byte (ID of the sent message)
4 00 Number of data bytes
5 03 Checksum
The confirmation message is sent in response to a command sent to
the device. The ID byte and the check-sum will change with different
commands but the format will remain the same. If the checksum is not
correct an error message is sent. Its format is covered at the end of this
document.
To stop receiving data from the J1708 bus send the following
command to the HDV100A3.