B&B Electronics 1939STB TV Converter Box User Manual


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1939STB4600 Manual Appendix A A-1
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104
B&B Electronics Ltd – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph +353 91 792444 – Fax +353 91 792445
Appendix A. The Extended CAN / SAE-J1939 Message Frame
Arbitration Field Control Field Data
Field
CRC
Field
Ack
Field
EOF
Identifier (11) bits Identifier Extension (18 Bits) DLC
1 2 3 4 5 6 7 8 9 1
0
1
1
1 234567891
0
1
1
1
2
1
3
1
4
1
5
1
6
1
7
1
8
1 2 3 4 8 bytes
64 bits
2 bytes
16 bits
S
O
F
Priority
(3 bits)
R
1
D
P
PDU Format (PF)
(8 bits)
S
R
S
I
D
E
PF
Cont
PDU Specific (PS)
(8 Bits)
Source Address
(8 Bits)
R
T
R
R
1
R
0
1 2 3 4 5 6 7 8 9 1
0
1
1
1
2
1
3
1
4
1
5
1
6
1
7
1
8
1
9
2
0
2
1
2
2
2
3
2
4
2
5
2
6
2
7
2
8
2
9
3
0
3
1
3
2
3
3
3
4
3
5
3
6
3
7
3
8
3
9
The table above shows a comparison between the SAE-J1939 message frame and the extended CAN message frame.
The bold line separates the upper and lower parts of the table. The upper half of the table shows the CAN data frame labels and the lower part of the table contains
the SAE-J1939 data labels. The areas that are in gray are controlled by the CAN controller and cannot be altered.
The CAN extended frame is made up of 6 fields: Arbitration, Control, Data, CRC, ACK, EOF. The arbitration field is subdivided into two fields of 11 and 18 bit identifiers.
CAN uses these fields to determine both identification and priority.
The SAE-J1939 specification future subdivides the arbitration field as follows:
Priority 3 bits with a value of 0 to 7 - with 0 having the highest priority.
R1 1 bit. This bit is reserved by the SAE for future use and should be set to 0.
DP Data Page 1bit. Sets an auxiliary page of parameter groups.
PDU-Format 8 bit. One of the fields that makes up the Parameter Group Number.
PDU-Specific 8 bit. The second field the makes up the Parameter Group Number.
Source Address 8 bit. The address of the sending/receiving node.
The fields above are required to send a message on the SAE-J1939 bus. Additionally the 8 byte data field may or may not contain data.
An expanded view of the Arbitration field is shown on the following page.
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