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LH75400/01/10/11 (Preliminary) User's Guide
Controller Area Network
Table 22-30. Transmit Frame/Receive Frame Definitions
NAME
DESCRIPTION
///
Reserved
Frame Format Selects the type of frame format to be used for transmission.
FF
0 = Uses Standard Frame Format.
1 = Uses Extended Frame Format.
Remote Transmission Request
RTR
0 = Indicates a data frame, as defined in the CAN protocol.
1 = Indicates a remote frame.
Don't care, but 0 is recommended for compatibility with the Receive Buffer, in
1
x
case the Self-Reception or Self Test Option is used.
Data Length Code Specifies the number of data bytes included in message
being sent. The maximum number of data bytes that can be included in a frame
is eight; therefore, values greater than eight are interpreted as eight automatical-
ly. Consult the CAN 2.0B specification for a complete description about data-
DLC.3 - DLC.0
length encoding. Note, too, that although no data bytes are transmitted from the
local host in the case of a remote frame transmission, the data length of the re-
mote frame should still be specified to avoid bus errors if two CAN Controllers
start a remote frame transmission with the same identifier simultaneously.
Identifier Acts as the message's name, is used in a receiver for acceptance
filtering, and determines the bus access priority. The lower the binary value of
the identifier the higher the priority.
ID
• In SFF, the identifier consists of 11 bits (ID.28 to ID.18).
• In EFF, messages the identifier consists of 29 bits (ID.28 to ID.0). ID.28 is the
most-significant bit and is transmitted first on the bus.
Data Field Comprises the number of data bytes defined by the data length
Data Field
code. The most-significant bit of data byte 1 at CAN address 0xFFFC5064
(SFF) or CAN address 0xFFFC5084 (EFF) is transmitted first.
6/17/03
22-25
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