B&B Electronics HVD100A3 manual J1708 Commands

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	Byte Value	Byte Function
Number	(hex)
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	Byte Value	Byte Function
Number	(hex)
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.

12	HDV100A3 Command & Response Manual-1306cr
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