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Chapter 16
FCAN Controller
User’s Manual U16702EE3V2UD00
16.2 CAN
Protocol
CAN (Controller Area Network) is a high-speed multiplex communication protocol for real-time commu-
nication in automotive applications (class C). CAN is prescribed by ISO 11898. For details, refer to the
ISO 11898 specifications.
The CAN specification is generally divided into two layers: a physical layer and a data link layer. In turn,
the data link layer includes logical link and medium access control. The composition of these layers is
illustrated below.
Figure 16-2:
Composition of Layers
Note:
CAN controller specification
16.2.1 Frame
format
(1)
Standard format frame
•
The standard format frame uses 11-bit identifiers, which means that it can handle up to
2,048 messages.
(2)
Extended format frame
•
The extended format frame uses 29-bit (11 bits + 18 bits) identifiers, which increases the
number of messages that can be handled to 2,048
¥
218 messages.
•
An extended format frame is set when “recessive level” (CMOS level of “1”) is set for both the
SRR and IDE bits in the arbitration field.
Physical layer
Prescription of signal level and bit description
Data link
layer
Note
·
Logical link control (LLC)
·
Medium access control (MAC)
·
Acceptance filtering
·
Overload report
·
Recovery management
·
Data capsuled/not capsuled
·
Frame coding (stuffing/no stuffing)
·
Medium access management
·
Error detection
·
Error report
·
Acknowledgement
·
Seriated/not seriated
Higher
Lower
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