Page
29
of
43
6.2
Structure of the CAN payload
The following table shows the structure of a CAN payload encapsulated in a 100BASET1_SPY RAW
frame:
Note:
The Control Field byte contains the following information about the CAN reception state:
7
6
5
4
3
2
1
0
Reserved
CRC
Reserved
IDE
Reserved
RTR
Reserved
ACK
o
ACK: A ‘1’ value in this bit indicates if there was an acknowledge during the reception of the
CAN frame.
o
RTR: A ‘1’ value in this bit indicates if the CAN frame is a remote frame. In this case, the
LENGTH field will be 0x00, and there is no any payload.
o
IDE: A ‘1’ value in this bit indicates if the CAN frame ID is in standard (11 bits) or extended
format (29 bits).
o
CRC: A ‘1’ value in this bit indicates if there was any CAN CRC error during the reception of
the CAN frame.
Note:
The Zero Padding length depends of the Length Field. There will be Zero Padding if CAN
Payload length is less than the minimum RAW Ethernet Payload size (46 bytes). There is zero padding
if CAN Length is less than 48 bytes.
The following image shows an example of a CAN payload frame encapsulated in a 100BASET1_SPY
RAW frame, without zero padding:
Field Name
No. Of Bytes Value
Control Field
1
Contains information about the CAN reception
state
Identifier
4
Received CAN Identifier
LENGTH
1
Length of the CAN frame payload (in bytes)
PAYLOAD
0 to 64
Received Can Payload
CRC
3
Received CAN CRC
Zero Padding
X