SH7052 datasheet(565/919 Pages) RENESAS

565 / 919 page

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1. Transmission order determined by mailbox number priority

2. Transmission order determined by message identifier priority

When the mailbox number 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 message identifier 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] to 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.

15.3.3

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 15.7.

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

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

SH7052 Datasheet(PDF) 565 Page - Renesas Technology Corp