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Section 20 Controller Area Network
Page 1060 of 2108 R01UH0134EJ0400 Rev. 4.00
Sep 24, 2014
SH7262 Group, SH7264 Group
SOFEOF IntermSOF SOFEOF Interm
RCAN-TL1
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
MessageBus Idle
CAN bus
state
Message
Tx Arb for
Frame-1
Tx/Rx Arb for
Frame-1
Tx/Rx Arb for
Frame-3/2
Tx Arb for
Frame-3
Tx Arb for
Frame-3
Tx/Rx Arb for
Frame-3
1-1 1-2 2-1 2-2 3-1 3-2
Figure 20.17 Internal Arbitration for transmission
This module 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, this module 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, this module 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, this module 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.