7 Layer 2 Communication Mode (11/29 bit ID)
7.1 [BFM #100 to #399] Sending/Receiving Pre-defined Layer 2 Messages
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-J1939 User's Manual
1
Introduc
tion
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Specifi
cations
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Inst
allati
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Wi
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Al
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ca
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Buf
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Memor
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J1939 C
omms
Mode
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La
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C
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M
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PL
C RUN>
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Co
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Comm
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Proc
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2. When receiving messages
The CAN-ID, status/control flags and data bytes of each message are as follows.
Note
In case more than one ID can pass the filter set in BFM #1100 to #1267, the received CAN-ID might change.
The CAN-ID, DLC and data of the latest received message will always be displayed.
For Layer 2 message configuration in BFM #1100 to #1267, refer to Section 7.2
1) CAN-ID
The 32 bit source CAN-ID of the received Layer 2 message is stored. Values are as follows:
- 11 bit mode: 0 to H000007FF
- 29 bit mode: 0 to H1FFFFFFF
For the function mode, refer to Section 5.4
*1.
The "n" corresponds to the Layer 2 message number.
2) Status/Control Flags
*2.
If bit 8 of the Status/Control Flags is ON, a new frame including new data has been received and
stored. If bit 9 is ON but bit 8 is OFF, the same message (same ID, DLC and data) has been
received. If bit 10 is ON, at least one more frame has been stored in this message buffer while bit 8
was ON which caused an overflow condition.
3) Data bytes
The data received of length specified by DLC is stored.
In case the received DLC is less than 8, unused data bytes are set to H00.
Function Mode
Description
Layer 2 communication
(11 bit ID) mode
CAN-ID is stored in the 11 bits, bit 0 to 10, in the CAN-ID n
*1
LW.
In this function mode, CAN-ID n
*1
HW does not used.
Layer 2 communication
(29 bit ID) mode
CAN-ID is stored in the 29 bits, bit 0 to 28, in the CAN-ID n
*1
LW and CAN-ID n
*1
HW.
Handle CAN-ID n
*1
LW and CAN-ID n
*1
HW by 32 bit instructions.
High Byte/Low Byte
Description
High byte
H00:
New data is not received.
Bit 8:
ON when new data is received.
Bit 9:
ON when new frame is received.
Bit 10:
ON when overflowing.
*2
Low byte
Data length count (DLC) of the received CAN frame.
Status/Control
Flags
Receive messages only
New frame
no new data
New frame
new data
New frame
no new data
overflow occur
New frame
new data
overflow occur
No data received
New data (bit 8)
OFF
ON
ON
ON
- (Do not care)
New frame (bit 9)
ON
ON
OFF
ON
OFF
Overflow (bit 10)
OFF
OFF
ON
ON
- (Do not care)
