PXN20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor 29-1
Chapter 29
Controller Area Network (FlexCAN)
29.1 Introduction
The PXN20 contains as many as six controller area network (FlexCAN) blocks. Each FlexCAN module
is a communication controller implementing the CAN protocol according to Bosch Specification version
2.0B and ISO Standard 11898. The CAN protocol is used as a serial data bus, meeting the specific
requirements of this field: real-time processing, reliable operation in the EMI environment of a vehicle,
cost-effectiveness and required bandwidth.
NOTE
The FlexCAN_F block is not implemented on the PXN21.
The CAN protocol interface (CPI) sub-module 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) sub-module handles message buffer
selection for reception and transmission, taking care of arbitration and ID matching algorithms. The bus
interface unit (BIU) sub-module controls the access to and from the internal interface bus, to establish
connection to the CPU and other blocks. Clocks, address and data buses, interrupt outputs, and test signals
are accessed through the bus interface unit.
29.1.1 Block Diagram
A simplified block diagram of the FlexCAN illustrates the functionality and interdependence of major
sub-blocks (see Figure 29-1).
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