R01UH0823EJ0100 Rev.1.00
Page 1266 of 1823
Jul 31, 2019
RX23W Group
36. CAN Module (RSCAN)
Bus off: Isolated from CAN communication.
When the CTRL.CHMDC[1:0] bits are set to 00b, the channel transitions to channel communication mode. After that,
when 11 consecutive recessive bits have been detected, the STSL.COMSTS flag becomes 1 (communication is ready)
and transmission and reception are enabled on the CAN network as an active node. At this time, transmission and
reception of messages can be started.
(5) Bus Off State
A channel transitions to the bus off state according to the transmit/receive error counter increment/decrement rules of the
ISO 11898-1 standard.
How to return from the bus off state is set by the CTRH.BOM[1:0] bits.
When CTRH.BOM[1:0] = 00b:
Bus off recovery is compliant with the ISO 11898-1 standard. After 11 consecutive recessive bits have been
detected 128 times, a channel returns from the bus off state to the CAN communication ready state (error active
state).
At that time, the STSH.TEC[7:0] and STSH.REC[7:0] flags are initialized to 00h and the ERFLL.BORF flag
becomes 1 (bus off recovery is detected). When the CTRL.CHMDC[1:0] bits are set to 10b (channel halt mode) in
the bus off state, the channel transitions to channel halt mode after bus off recovery has been completed (11
consecutive recessive bits have been detected 128 times).
When CTRH.BOM[1:0] = 01b:
When a channel transitions to the bus off state, the CTRL.CHMDC[1:0] bits are set to 10b and the channel
transitions to channel halt mode. At that time, the STSH.TEC[7:0] and STSH.REC[7:0] flags are initialized to 00h
but the ERFLL.BORF flag is not set to 1.
When CTRH.BOM[1:0] = 10b:
When a channel has transitioned to the bus off state, the CTRL.CHMDC[1:0] bits are set to 10b. After bus off
recovery has been completed (11 consecutive recessive bits have been detected 128 times), the channel transitions
to channel halt mode. At that time, the STSH.TEC[7:0] and STSH.REC[7:0] flags are initialized to 00h and the
ERFLL.BORF flag becomes 1.
When CTRH.BOM[1:0] = 11b:
When the CHMDC[1:0] bits are set to 10b in the bus off state, the channel transitions to channel halt mode before
bus off recovery is completed. At that time, the STSH.TEC[7:0] and STSH.REC[7:0] flags are initialized to 00h but
the ERFLL.BORF flag is not set to 1.
However, the BORF flag becomes 1 if a CAN module transitions to error active state (by detecting 128 times of 11
consecutive recessive bits) before the CTRL.CHMDC[1:0] bits are set to 10b.
If the channel transitions to channel halt mode simultaneously when the program writes a value to the
CTRL.CHMDC[1:0] bits, writing by the program takes precedence. An automatic transition to channel halt mode when
the CTRH.BOM[1:0] bits are set to 01b or 10b is made only when the CTRL.CHMDC[1:0] bits are 00b (channel
communication mode).
Furthermore, setting the CTRL.RTBO bit to 1 allows forcible return from the bus off state. As soon as the CTRL.RTBO
bit is set to 1, the state changes to the error active state. After 11 consecutive recessive bits have been detected, the
condition of CAN module becomes ready for communication. In this case, the ERFLL.BORF flag is not set to 1 and the
STSH.TEC[7:0] and STSH.REC[7:0] flags are initialized to 00h. Write 1 to the CTRL.RTBO bit when the
CTRH.BOM[1:0] value is 00b.