Can Protocol; Frame Format; Figure 18-2: Composition Of Layers - NEC V850E/PH2 User Manual

18.2 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.
Higher
Data link
layer Note
Physical layer
Lower
Note: CAN Controller specification

18.2.1 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 × 2
• 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.
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Chapter 18 AFCAN Controller

Figure 18-2: Composition of Layers

·
Logical link control (LLC)
·
Medium access control (MAC)
User's Manual U16580EE3V1UD00
·
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
Prescription of signal level and bit description
18
messages.