SH7760 Datasheet, PDF (868/1345 Pages) Renesas Technology Corp – SuperHTM RISC engine

When the HCAN2 recognizes the end of Arbitration field while receiving a message, it starts
comparing the received identifier to the identifiers set in Mailboxes, starting from Mailbox 31
down to Mailbox 0. It first checks the MBC if it is configured as a receive box, and reads LAFM,
and reads the CAN-ID of Mailbox 31 (if configured as receive) to finally compares them to the
received ID. If it does not match, the same check takes place at Mailbox 30 (if configured as a
receive). Once HCAN2 finds a matching identifier, it stores the number of Mailbox [N] into an
internal buffer, stops the search, and gets back to idle state, waiting for an EndOfFrame (EOF) to
come. When an EOF is notified by the CAN interface logic, HCAN2 this time only reads the
MBC, LAFM and CAN-ID of Mailbox [N] to confirm the matching condition again (i.e., there has
been no modification to the configuration of Mailbox [N]). This re-confirmation guarantees the
data consistency even when a Mailbox is re-configured during receiving message. If it still
matches, then the message is written or abandoned, depending on the NMC bit. If it is written into
the corresponding Mailbox, including the CAN-ID, i.e., there is a possibility that the CAN-ID is
overwritten by a different CAN-ID of the received message due to the LAFM used. This also
implies that, if the identifier of the received message matches the ID + LAFM of 2 or more
Mailboxes, the higher numbered Mailbox will always store the relevant messages and the lower
numbered Mailbox will never receive messages. Therefore, the settings of the identifiers and
LAFMs need to be carefully selected.
22.6.5 Reconfiguration of Mailbox
When re-configuration of Mailboxes is required, the following procedures should be taken.
(1) Change ID of transmit box or Change transmit box to receive box
Confirm that the corresponding CANTXPR is not set. The identifier and corresponding MBC
field can be changed at any time. When both of them need to be changed, please change the
identifier first and then the corresponding MBC field.
(2) Change ID of receive box or Change receive box to transmit box
• Method-1: Using Halt Mode
The advantage of this method is that HCAN2 will not lose a message if the message is
currently on the CAN bus and the HCAN2 is a receiver. HCAN2 will be in Halt Mode after
completing of the reception. The disadvantage is that it might take long if HCAN2 is
receiving a message (as the transmission to the halt state is delayed until the end of the
reception), and also HCAN2 will not be able to receive/transmit messages during Halt
mode.
Rev. 1.0, 02/03, page 818 of 1294