K60P100M100SF2RM Datasheet, PDF (1357/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

• When FlexCAN exits Bus Off state.
• Upon leaving Freeze Mode or Low Power Mode.
Chapter 48 CAN (FlexCAN)
If the arbitration process does not manage to evaluate all Mailboxes before the CAN bus
has reached the first bit of the Intermission field the temporary arbitration winner is
invalidated and the FlexCAN will not compete for the CAN bus in the next opportunity.
The arbitration process selects the winner among the active Tx Mailboxes at the end of
the scan according to both CTRL1[LBUF] and MCR[LPRIO_EN] bits settings.
48.4.2.1 Lowest number Mailbox first
If CTRL1[LBUF] bit is asserted the first (lowest number) active Tx Mailbox found is the
arbitration winner. MCR[LPRIO_EN] bit has no effect when CTRL1[LBUF] is asserted.
48.4.2.2 Highest priority Mailbox first
If CTRL1[LBUF] bit is negated then the arbitration process searches the active Tx
Mailbox with the highest priority, which means that this Mailbox’s frame would have a
higher probability to win the arbitration on CAN bus with multiple nodes driving each Tx
Mailbox’s frame at the same time.
The sequence of bits considered for this arbitration is called the arbitration value of the
Mailbox. The highest priority Tx Mailbox is the one that has the least arbitration value
among all Tx Mailboxes.
If two or more Mailboxes have equivalent arbitration values the lowest number Mailbox
is the arbitration winner.
The composition of the arbitration value depends on MCR[LPRIO_EN] bit setting.
48.4.2.2.1 Local Priority disabled
If MCR[LPRIO_EN] bit is negated the arbitration value is built in the exact sequence of
bits as they would be transmitted in a CAN frame (see the following table) in such a way
that the Local Priority is disabled.
K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc.
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