B&B Electronics Command Response Protocol HVD100A3 Manuale Utente Scaricare il pdf (Pagina 16)

12 HDV100A3 Command & Response Manual

B&B Electronics -- 707 Dayton Rd. -- PO Box 1040 -- Ottawa, IL 61350

PH (815) 433-5100 -- FAX (815) 433-5104

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

Start of frame

The number of control bytes

ID byte 01= J1708

Function code 11 hex start receive

Number of data bytes (00 place holder)

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

Start of frame byte

Control byte

ID byte (ID of the sent message)

Number of data bytes

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.

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B&B Electronics Command Response Protocol HVD100A3 Manuale Utente Pagina 16