B&B Electronics Command Response Protocol HVD100A3 Manuale Utente Scaricare il pdf (Pagina 25)

HDV100A3 Command & Response Manual 21 Cover Page

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

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

Data messages received from the HDV100A3 operating in the J1939 mode,

is formatted as follows:

Control Field

Data Field

Start

Frame

# of

Control

bytes

Contr

Byte

Time Stamp

4 Bytes

# of

Data

Bytes

Arbitration

Field

# of

Data

Bytes

Message

Bus Data

Up to 8 Bytes

Check

sum

msb

lsb

The message starts with 01. The number of control bytes is 05. Next is the

control byte 02, followed by the time stamp, four bytes, with msb first. The

number of data bytes is the number of bytes to follow excluding itself and the

checksum byte. Next is a four byte that contains the arbitration field. J1939

divides this field for different functions show in the chart below. The number

of data bytes sent by the bus is next. This will be a value between 0 and 8.

Next is the bus data followed by the checksum byte.

Arbitration Field (Y1, Y2, Y3, Y4)

The first byte Y1 contains the most significant bits in the J1939 arbitration

field. It is followed by Y2, Y3 and Y4. J1939 assigns different function to

the arbitration field that must be observed by the user. There is a work sheet

included on page 33 to help set up this field.

Arbitration Byte

Arbitration Bit

J1939 Arbitration Field

Bit Position

J1939 Function

Priority

bits

PDU Format

PDU Specific

Source Address

1 2 ... 20 21 22 23 24 25 26 27 28 29 30 31

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