Datasheet
20. CAN – Controller Area Network
20.1. Features
• Full CAN controller
• Fully compliant with CAN standard rev 2.0 A and rev 2.0 B
• Six MOb (Message Object) with their own:
– 11 bits of Identifier Tag (rev 2.0 A), 29 bits of Identifier Tag (rev 2.0 B)
– 11 bits of Identifier Mask (rev 2.0 A), 29 bits of Identifier Mask (rev 2.0 B)
– Eight bytes data buffer (static allocation)
– Tx, Rx, frame buffer or automatic reply configuration
– Time stamping
• 1Mbit/s maximum transfer rate at 8MHz
• TTC timer
• Listening mode (for spying or autobaud)
20.2. Overview
The Controller Area Network (CAN) protocol is a real-time, serial, broadcast protocol with a very high
level of security. The Atmel ATmega16M1/32M1/64M1 CAN controller is fully compatible with the CAN
Specification 2.0 Part A and Part B. It delivers the features required to implement the kernel of the CAN
bus protocol according to the ISO/OSI Reference Model:
• The data link layer
– the Logical Link Control (LLC) sublayer
– the Medium Access Control (MAC) sublayer
• The physical layer
– the Physical Signalling (PLS) sublayer
– not supported - the Physical Medium Attach (PMA)
– not supported - the Medium Dependent Interface (MDI)
The CAN controller is able to handle all types of frames (data, remote, error and overload) and achieves a
bitrate of 1Mbit/s.
20.3. CAN protocol
The CAN protocol is an international standard defined in the ISO 11898 for high speed and ISO 11519-2
for low speed.
20.3.1. Principles
CAN is based on a broadcast communication mechanism. This broadcast communication is achieved by
using a message oriented transmission protocol. These messages are identified by using a message
identifier. Such a message identifier has to be unique within the whole network and it defines not only the
content but also the priority of the message.
The priority at which a message is transmitted compared to another less urgent message is specified by
the identifier of each message. The priorities are laid down during system design in the form of
Atmel ATmega16M1/32M1/64M1 [DATASHEET]
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