SH7261 datasheet(895/1348 Pages) RENESAS

895 / 1348 page

Section 19 Controller Area Network (RCAN-ET) [R5S72611] [R5S72613]

Rev. 2.00 Sep. 07, 2007 Page 863 of 1312

REJ09B0320-0200

19.6.3

Message Transmission Sequence

(1)

Message Transmission Request

The following sequence is an example to transmit a CAN frame onto the bus. As described in the

previous register section, please note that IRR8 is set when one of the TXACK or ABACK bits is

set, meaning one of the Mailboxes has completed its transmission or transmission abortion and is

now ready to be updated for the next transmission, whereas, the GSR2 means that there is

currently no transmission request made (No TXPR flags set).

Yes

RCAN-ET is in Normal Mode

(MBC[n] = 0)

Write '1' to the TXPR[n] bit

at any desired time

Internal Arbitration

'n' Highest Priority?

Transmission Start

Mailbox[n] is ready

to be updated for

next transmission

Clear TXACK[n]

TXACK[n] set?

CAN Bus

Arbitration

Acknowledge Bit

CAN Bus

IRR8 set?

Update Message Data of

Mailbox[n]

Monitor for the next interrupt

Note: n = 0 to 15 (mailbox number)

Figure 19.9 Transmission Request

(2)

Internal Arbitration for Transmission

The following diagram explains how RCAN-ET manages to schedule transmission-requested

messages in the correct order based on the CAN identifier. 'Internal arbitration' picks up the

highest priority message amongst transmit-requested messages.

SH7261 Datasheet(PDF) 895 Page - Renesas Technology Corp