MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
Freescale Semiconductor 22-3
The CAN protocol interface (CPI) manages the serial communication on the CAN bus, requesting RAM
access for receiving and transmitting message frames, validating received messages and performing error
handling. The message buffer management (MBM) handles message buffer selection for reception and
transmission, taking care of arbitration and ID matching algorithms. The bus interface unit (BIU) controls
the access to and from the internal interface bus, in order to establish connection to the CPU and to any
other modules. Clocks, address and data buses, interrupt outputs and test signals are accessed through the
bus interface unit.
22.1.3 Features
The FlexCAN2 module includes these distinctive features:
• Based on and includes all existing features of the Freescale TouCAN module
• Full implementation of the CAN protocol specification, version 2.0B
— Standard data and remote frames
— Extended data and remote frames
— Data length of 0 to 8 bytes
— Programmable bit rate up to 1 Mb/sec
• Content-related addressing
• 64 flexible message buffers of 0 to 8 bytes data length
• Each MB configurable as RX or TX, all supporting standard and extended messages
• Includes 1024 bytes of RAM used for MB storage
• Programmable clock source to the CAN protocol interface, either system clock or oscillator clock
• Listen-only mode capability
• Programmable loop-back mode supporting self-test operation
• Three programmable mask registers
• Programmable transmit-first scheme: lowest ID or lowest buffer number
• Time stamp based on 16-bit free-running timer
• Global network time, synchronized by a specific message
• Maskable interrupts
• Independent of the transmission medium (an external transceiver is assumed)
• Multi master concept
• High immunity to EMI
• Short latency time due to an arbitration scheme for high-priority messages
22.1.4 Modes of Operation
The MPC5553/MPC5554 supports four FlexCAN functional modes: normal, freeze, listen-only and
loop-back. Just one of the low power modes—module disabled—is supported.
22.1.4.1 Normal Mode
In normal mode, the module operates receiving and/or transmitting message frames, errors are handled
normally and all the CAN protocol functions are enabled. In the MPC5553/MPC5554, there is no
distinction between user and supervisor modes.
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