SH7059 Datasheet, PDF (569/1042 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

17. Controller Area Network-II (HCAN-II)
17.7.6 Reconfiguration of Mailboxes
When reconfiguration of mailboxes is required, the following procedures should be taken.
Change ID of Transmit Box or Change Transmit Box to Receive Box: Confirm that the corresponding TXPR is not
set. The ID or corresponding MBC bit can be changed at any time. When both need to be changed, change the ID first and
then change the corresponding MBC bit.
Change ID of Receive Box or Change Receive Box to Transmit Box:
Method-1: Using Halt Mode
The advantage of this method is that the HCAN will not lose a message even if the message is on the CAN bus and the
HCAN is a receiver. The HCAN-II will be in halt mode after completing the reception. The disadvantage is that it might
take long if the HCAN is receiving a message (as the transition to halt mode is delayed until the end of the reception), and
also the HCAN will not be able to receive/transmit messages during halt mode.
Method-2: Without Using Halt Mode
The advantage of this method is that the reconfiguration is done immediately, and the software overhead will be less as
there is no interrupt. RXPR needs to be read before and after the reconfiguration. This is because to check if a message is
received or not during this period. Note that MBIMR does not prevent the IRR1 from being set but simply prevents the
interrupt signal from being generated. If a message is received, it is unknown if the received message is for the previous
ID or for the new ID. Therefore, if a message is received during this period, it is better to abandon this message, and this is
the disadvantage of this method.
Rev.3.00 Mar. 12, 2008 Page 479 of 948
REJ09B0177-0300