SH7261 Datasheet, PDF (896/1348 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7260 Series

Section 19 Controller Area Network (RCAN-ET) [R5S72611] [R5S72613]
CAN bus
state
RCAN-ET
scheduler state
Scheduler
start point
TXPR/TXCR/
Error/Arb-Lost
Set Point
Bus Idle
Transmission
Frame-1
SOF Message EOF Interm SOF
Reception
Frame-2
Message
Transmission
Frame-3
EOF Interm SOF
CTx Arb for CTx/CRx Arb for CTx Arb for
Frame-1
Frame-1
Frame-3
CTx/CRx Arb for CTx Arb for
Frame-3/2
Frame-3
CTx/CRx Arb for
Frame-3
1-1
1-2
2-1
2-2
3-1
3-2
Interm:
SOF:
EOF:
Message:
Intermission Field
Start Of Frame
End Of Frame
Arbitration + Control + Data + CRC + Ack Field
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.
Rev. 2.00 Sep. 07, 2007 Page 864 of 1312
REJ09B0320-0200