NXP Semiconductors MWCT101 S Series, Reference Manual

Page: 1673 / 1761

If NMATCH is greater than four, the last four matching messages are stored in the
WMBs. The WMB index indicates the arrival order. The last message is stored in
WMB3.
Only the valid data bytes of the incoming match message are stored in the data field of
WMBs. The non-valid data bytes are read as zero. If DLC=0 and RTR=1, the data field is
filled with zeroes. In any of the above cases, the wakeup interrupt is generated just when
the filtering criteria is completed and CTRL1_PN[WUMF_MSK] is enabled.
When a non-match wakeup event occurs (timeout or external) and MCOUNTER register
is equal to or greater than four, the message stored in WMB0 does not have valid content.
WMB0 is used as a buffer for the current message in the CAN bus. Messages received
during Pretended Networking mode don't have time stamps, and the respective field in
the WMB structure must be ignored.
Under low power mode (Stop), all processes are shut down except for the PN
functionality inside CAN_PE sub-block, which is kept clocked by the oscillator clock
(see
Clock domains and restrictions ). FlexCAN continues to receive Rx incoming
messages but only compares them to the predefined target values and in accordance with
the selected filtering criteria. The matching, arbitration, move-in and move-out processes,
normally available in Normal mode, are not performed under Pretended Networking
mode.
FlexCAN under Pretended Networking reacts to messages on the CAN bus in the same
manner as in Normal mode (that is, it generates acknowledge bits, detect and count
errors, etc.).
49.5.6 Move process
There are two types of move process: move-in and move-out.
49.5.6.1 Move-in
The move-in process is the copy of a message received by an Rx SMB to an Rx mailbox
or FIFO that has matched it. If the move destination is the Rx FIFO, attributes of the
message are also copied to the CAN_RXFIR FIFO. Each Rx SMB has its own move-in
process, but only one is performed at a given time as described ahead. The move-in starts
only when the message held by the Rx SMB has a corresponding matching winner (see
Matching process ) and all of the following conditions are true:
• The CAN bus has either reached or already gone past:
Chapter 49 FlexCAN
MWCT101xS Series Reference Manual, Rev. 3, 07/2019
NXP Semiconductors 1673