Datasheet

20.7.2. 16-bit timer
This timer starts counting from 0x0000 when the CAN controller is enabled (ENFG bit). When the timer
rolls over from 0xFFFF to 0x0000, an interrupt is generated (OVRTIM).
20.7.3. Time triggering
Two synchronization modes are implemented for TTC (TTC bit):
• synchronization on Start of Frame (SYNCTTC=0)
• synchronization on End of Frame (SYNCTTC=1)
In TTC mode, a frame is sent once, even if an error occurs.
20.7.4. Stamping message
The capture of the timer value is done in the MOb which receives or sends the frame. All managed MOb
are stamped, the stamping of a received (sent) frame occurs on RxOk (TXOK).
20.8. Error management
20.8.1. Fault confinement
The CAN channel may be in one of the three following states:
• Error active (default):
The CAN channel takes part in bus communication and can send an active error frame when the
CAN macro detects an error
• Error passive:
The CAN channel cannot send an active error frame. It takes part in bus communication, but when
an error is detected, a passive error frame is sent. Also, after a transmission, an error passive unit
will wait before initiating further transmission
• Bus off:
The CAN channel is not allowed to have any influence on the bus
For fault confinement, a transmit error counter (TEC) and a receive error counter (REC) are implemented.
BOFF and ERRP bits give the information of the state of the CAN channel. Setting BOFF to one may
generate an interrupt.
Figure 20-12. Line Error mode.
ERRP = 1
ERRP = 1
BOFF = 0
BOFF = 0
Error
Error
active
active
Error
Error
passive
passive
Bus
Bus
off
off
TEC > 127 or
TEC > 127 or
REC > 127
REC > 127
128 occurrences
128 occurrences
of 11 consecutive
of 11 consecutive
recessive bit
recessive bit
Reset
Reset
interrupt - BOFFIT
interrupt - BOFFIT
TEC > 255
TEC > 255
TEC < 127 and
TEC < 127 and
REC < 127
REC < 127
ERRP = 0
ERRP = 0
BOFF = 0
BOFF = 0
ERRP = 0
ERRP = 0
BOFF = 1
BOFF = 1
Note: More than one REC/TEC change may apply during a given message transfer.
Atmel ATmega16M1/32M1/64M1 [DATASHEET]
Atmel-8209F-ATmega16M1/32M1/64M1_Datasheet_Complete-10/2016
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