SH7261 datasheet(896/1348 Pages) RENESAS

896 / 1348 page

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

Rev. 2.00 Sep. 07, 2007 Page 864 of 1312

REJ09B0320-0200

SOF

EOF Interm

SOF

EOF Interm

RCAN-ET

scheduler state

Scheduler

start point

TXPR/TXCR/

Error/Arb-Lost

Set Point

Interm:

Intermission Field

SOF:

Start Of Frame

EOF:

End Of Frame

Message:

Arbitration + Control + Data + CRC + Ack Field

Transmission

Frame-1

Reception

Frame-2

Transmission

Frame-3

Message

Bus Idle

CAN bus

state

Message

CTx Arb for

Frame-1

CTx/CRx Arb for

Frame-1

CTx/CRx Arb for

Frame-3/2

CTx Arb for

Frame-3

CTx Arb for

Frame-3

CTx/CRx Arb for

Frame-3

1-1

1-2

2-1

2-2

3-1

3-2

Figure 19.10 Internal Arbitration for transmission

The RCAN-ET has two state machines. One is for transmission, and the other is for reception.

1-1: When a TXPR bit(s) is set while the CAN bus is idle, the internal arbitration starts running

immediately and the transmission is started.

1-2: Operations for both transmission and reception starts at SOF. Since there is no reception

frame, RCAN-ET becomes transmitter.

2-1: At crc delimiter, internal arbitration to search next message transmitted starts.

2-2: Operations for both transmission and reception starts at SOF. Because of a reception frame

with higher priority, RCAN-ET becomes receiver. Therefore, Reception is carried out instead

of transmitting Frame-3.

3-1: At crc delimiter, internal arbitration to search next message transmitted starts.

3-2: Operations for both transmission and reception starts at SOF. Since a transmission frame has

higher priority than reception one, RCAN-ET becomes transmitter.

Internal arbitration for the next transmission is also performed at the beginning of each error

delimiter in case of an error is detected on the CAN Bus. It is also performed at the beginning of

error delimiters following overload frame.

As the arbitration for transmission is performed at CRC delimiter, in case a remote frame request

is received into a Mailbox with ATX = 1 the answer can join the arbitration for transmission only

at the following Bus Idle, CRC delimiter or Error Delimiter.

Depending on the status of the CAN bus, following the assertion of the TXCR, the corresponding

Message abortion can be handled with a delay of maximum 1 CAN Frame.

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