UM0306 Controller area network (bxCAN)
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14.5.5 Message storage
The interface between the software and the hardware for the CAN messages is
implemented by means of mailboxes. A mailbox contains all information related to a
message; identifier, data, control, status and time stamp information.
Transmit mailbox
The software sets up the message to be transmitted in an empty transmit mailbox. The
status of the transmission is indicated by hardware in the CAN_TSR register.
Receive mailbox
When a message has been received, it is available to the software in the FIFO output
mailbox. Once the software has handled the message (e.g. read it) the software must
release the FIFO output mailbox by means of the RFOM bit in the CRFR register to make
the next incoming message available. The filter match index is stored in the MFMI field of
the CAN_RDTxR register. The 16-bit time stamp value is stored in the TIME[15:0] field of
CAN_RDTxR.
Table 42. Transmit mailbox mapping
Offset to Transmit Mailbox base
address
Register Name
0CAN_TIxR
4 CAN_TDTxR
8CAN_TDLxR
12 CAN_TDHxR
Table 43. Receive mailbox mapping
Offset to Receive Mailbox base
address (bytes)
Register Name
0CAN_RIxR
4 CAN_RDTxR
8CAN_RDLxR
12 CAN_RDHxR
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