h8s-2649 Renesas Electronics Corporation., h8s-2649 Datasheet - Page 511

• Manufacturer Part Number: h8s-2649
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2600 Series
• Manufacturer: Renesas Electronics Corporation.

14.8.10 HCAN TXCR Operation
1. When the transmit wait cancel register (TXCR) is used to cancel transmission of the message
2. When the bus-off state is entered while any mailbox is waiting for transmission with TXPR
[Conditions]
 The HRxD pin is tied to "1" because of a CAN bus error, etc.
 There is one or more mailboxes waiting for transmission or transmitting.
 Ongoing message transmission from a mailbox is canceled by TXCR.
If this occurs, the transmission is canceled but TXPR and TXCR continue to indicate a wrong
status telling that a message is being cancelled. As a result, transmission cannot be restarted
even after the HRxD pin is released from the tied state and the CAN bus has recovered. If there
are two or more messages for transmission, a message which is not being transmitted is
canceled and a message being transmitted retains its state.
To avoid this, take either of the following countermeasures.
[Countermeasures]
 Do not cancel transmission by TXCR. Transmission will be completed after the CAN bus
 To cancel transmission, write 1 to the corresponding bit in TXCR repeatedly until the bit
set, transmission cannot be canceled even if TXCR is set because the internal state machine
does not operate during the bus-off state. Because of this, on recovery from the bus-off state,
one message will be transmitted or the message will be canceled with a transmission error. For
message clearing on recovery from the bus-off state, take the following countermeasure.
[Countermeasure]
 Reset the HCAN during the bus-off period to clear the messages in the mailboxes waiting
in a mailbox waiting for transmission, the corresponding bit in TXCR and the transmit wait
register (TXPR) may not be cleared even after the transmission is canceled. This occurs when
the following conditions are all satisfied.
has recovered, then TXPR is cleared and the HCAN operates normally.
becomes 0. TXPR and TXCR are cleared, and the HCAN operates normally.
for transmission. To reset the HCAN, set the module stop bit (MSTPC3 in MSTPCRC) to 1
and then clear it. In this case, the HCAN is entirely reset. Therefore the initial settings must
be made again.
Section 14 Controller Area Network (HCAN)
Rev. 2.00 Dec. 05, 2005 Page 473 of 724
REJ09B0200-0200