DocID018909 Rev 11
RM0090
Controller area network (bxCAN)
1112
32.7.2 Time
triggered communication mode
In this mode, the internal counter of the CAN hardware is activated and used to generate the
Time Stamp value stored in the CAN_RDTxR/CAN_TDTxR registers, respectively (for Rx
and Tx mailboxes). The internal counter is incremented each CAN bit time (refer to
). The internal counter is captured on the sample point of the Start
Of Frame bit in both reception and transmission.
32.7.3 Reception
handling
For the reception of CAN messages, three mailboxes organized as a FIFO are provided. In
order to save CPU load, simplify the software and guarantee data consistency, the FIFO is
managed completely by hardware. The application accesses the messages stored in the
FIFO through the FIFO output mailbox.
Valid message
A received message is considered as valid
when
it has been received correctly according to
the CAN protocol (no error until the last but one bit of the EOF field)
and
It passed through
the identifier filtering successfully, see
Section 32.7.4: Identifier filtering
Figure 341. Receive FIFO states
EMPTY
Valid Message
FMP=0x00
FOVR=0
PENDING_1
FMP=0x01
FOVR=0
Received
PENDING_2
FMP=0x10
FOVR=0
PENDING_
3
FMP=0x11
FOVR=0
Valid Message
Received
Release
OVERRUN
FMP=0x11
FOVR=1
b
ox
Release
Mail
b
ox
Valid Message
Received
Valid Message
Received
Release
Mail
b
ox
Release
Mail
b
ox
Valid Message
Received
RFOM=1
RFOM=1
RFOM=1