Freescale Semiconductor MCF5480 - Manual (Page 573)

Introduction
MCF548x Reference Manual, Rev. 3
Freescale Semiconductor 21-3
bus. It can also provide protection against damage to the FlexCAN caused by a defective CAN bus or
defective stations.
21.1.3 Features
Following are the main features of the FlexCAN module:
• Full implementation of the CAN protocol specification version 2.0B
— Standard data and remote frames (up to 109 bits long)
— Extended data and remote frames (up to 127 bits long)
— 0–8 bytes data length
— Programmable bit rate up to 1 Mbps
— Content-related addressing
• Up to 16 flexible message buffers of 0–8 bytes data length, each configurable as Rx or Tx, all
supporting standard and extended messages
• Listen-only mode capability
• Three programmable mask registers: global (for MBs 0–13), special for MB14, and special for
MB15
• Programmable transmission priority scheme: lowest ID or lowest buffer number
• Time Stamp based on 16-bit free-running timer
• Global network time, synchronized by a specific message
• Programmable I/O modes
• Maskable interrupts
• Independent of the transmission medium (an external transceiver is assumed)
• Open network architecture
• Multimaster bus
• High immunity to EMI
• Short latency time due to an arbitration scheme for high-priority messages
21.1.4 Modes of Operation
21.1.4.1 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. User and supervisor modes differ in the access
to some restricted control registers.
21.1.4.2 Freeze Mode
Freeze mode is entered by:
• Setting CANMCR[FRZ], and
• Setting CANMCR[HALT], or by asserting the BKPT line.
Once entry into freeze mode is requested, the FlexCAN waits until an intermission or idle condition exists
on the CAN bus, or until the FlexCAN enters the error passive or bus off state. Once one of these
conditions exists, the FlexCAN waits for the completion of all internal activity like arbitration, matching,
move-in, and move-out. When this happens, the following events occur:
• The FlexCAN stops transmitting/receiving frames.