SH7055S Datasheet, PDF (599/1002 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH RISC engine Family/SH7000 Series

When the message identifier priority method is selected, if a number of messages are designated
as waiting for transmission (TXPR = 1), messages are stored in the transmit buffer in low-to-high
mailbox order (priority order: mailbox 1 > 15). CAN bus arbitration is then carried out for the
messages in the transmit buffer, and message transmission is performed when the bus is acquired.
When the mailbox number priority method is selected, if a number of messages are designated as
waiting for transmission (TXPR = 1), the message with the highest priority set in the message
identifier (MCx[5]–MCx[8]) is stored in the transmit buffer. CAN bus arbitration is then carried
out for the message in the transmit buffer, and message transmission is performed when the
transmission right is acquired. When the TXPR bit is set, internal arbitration is performed again,
and the highest-priority message is found and stored in the transmit buffer.
16.3.3 Transmit Mode
Message transmission is performed using mailboxes 1 to 15. The transmission procedure is
described below, and a transmission flowchart is shown in figure 16.9.
1. Initialization (after hardware reset only)
a. Clearing of IRR0 bit in interrupt register (IRR)
b. HCAN pin port settings
c. Bit rate settings
d. Mailbox transmit/receive settings
e. Mailbox initialization
f. Message transmission method setting
2. Interrupt and transmit data settings
a. Interrupt setting
b. Arbitration field setting
c. Control field setting
d. Data field setting
3. Message transmission and interrupts
a. Message transmission wait
b. Message transmission completion and interrupt
c. Message transmission abort
d. Message retransmission
Rev.2.0, 07/03, page 561 of 960