SH7047 Datasheet, PDF (512/764 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTMRISC engine Family/SH7000 Series

15.4.5 Mailbox Reconfiguration
Follow the procedure below to perform mailbox reconfiguration.
• Ensure that no corresponding TXPR is set that changes the transmit box ID or changes the
transmit box into the receive box. Any identifier and the corresponding MBC bit can be
changed any time. When changing both, change the identifier before changing the
corresponding MBC bit.
• Change the receive box ID or change the receive box into the transmit box.
<Method 1> Using halt mode
The advantage of this method is that no messages are lost as far as a message exists in the
CAN bus at that time and the HCAN2 becomes a receiver. Upon completion of reception, the
HCAN2 enters halt mode. The disadvantages are that reconfiguration takes time if the HCAN2
is in the middle of receiving messages (transition to halt mode is delayed until reception ends)
and no message reception/transmission is possible in halt mode.
<Method 2> Not using halt mode
The advantage of this method is that reconfiguration is immediately performed and the
software overhead is small as if no interrupts were existent. Reading RXPR, which is
necessary before and after reconfiguration, is for the purpose of checking if messages are
received during this period. Note that MBIMR simply prevents the interrupt signal from
occurrence instead of preventing the RXPR bit from being set. When any message is received,
it is unclear whether such message belongs to a previous or new ID. Accordingly, messages
received during this period should be discarded, which is the disadvantage of this method.
Rev. 2.00, 09/04, page 472 of 720