K60P100M100SF2RM Datasheet, PDF (1380/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

Functional Description
As an example, taking the case of 64 MBs, if the oscillator and peripheral clock
frequencies are equal and the CAN bit timing is programmed to have 8 time quanta per
bit, then the prescaler factor (PRESDIV + 1) should be at least 2. For prescaler factor
equal to one and CAN bit timing with 8 time quanta per bit, the ratio between peripheral
and oscillator clock frequencies should be at least 2.
48.4.9 Modes of Operation Details
The FlexCAN module has four functional modes (Normal Mode, Freeze Mode, Listen-
Only Mode and Loop-Back Mode) and three low power modes (Disable Mode, Doze
Mode and Stop Mode). See Modes of Operation for an introductory description of all
these modes of operation. The following sub-sections contain functional details on Freeze
mode and the low power modes.
CAUTION
“Permanent Dominant” failure on CAN Bus line is not
supported by FlexCAN. If a Low Power request or Freeze
Mode request is done during a “Permanent Dominant”, the
corresponding acknowledge can never be asserted.
48.4.9.1 Freeze Mode
This mode is requested by the CPU through the assertion of the HALT bit in the MCR
Register or when the MCU is put into Debug Mode. In both cases it is also necessary that
the FRZ bit is asserted in the MCR Register and the module is not in any of the low
power modes (Disable, Doze, Stop). The acknowledgement is obtained through the
assertion by the FlexCAN of FRZ_ACK bit in the same register. The CPU must only
consider the FlexCAN in Freeze Mode when both request and acknowledgement
conditions are satisfied.
When Freeze Mode is requested during transmission or reception, FlexCAN does the
following:
• Waits to be in either Intermission, Passive Error, Bus Off or Idle state
• Waits for all internal activities like arbitration, matching, move-in and move-out to
finish. A pending move-in is not taken into account.
• Ignores the Rx input pin and drives the Tx pin as recessive
• Stops the prescaler, thus halting all CAN protocol activities
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K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc.