918
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918
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The SLEEP signal in the CAN_SR register is automatically cleared once WAKEUP is set. The
WAKEUP signal is automatically cleared once SLEEP is set.
Reception is disabled while the SLEEP signal is set to one in the CAN_SR register. It is impor-
tant to note that those messages with higher priority than the last message transmitted can be
received between the LPM command and entry in Low-power Mode.
Once in Low-power Mode, the CAN controller clock can be switched off by programming the
chip’s Power Management Controller (PMC). The CAN controller drains only the static current.
Error counters are disabled while the SLEEP signal is set to one.
Thus, to enter Low-power Mode, the software application must:
– Set LPM field in the CAN_MR register
– Wait for SLEEP signal rising
Now the CAN Controller clock can be disabled. This is done by programming the Power Man-
agement Controller (PMC).
Figure 41-8.
Enabling Low-power Mode
41.7.5.2
Disabling Low-power Mode
The CAN controller can be awake after detecting a CAN bus activity. Bus activity detection is
done by an external module that may be embedded in the chip. When it is notified of a CAN bus
activity, the software application disables Low-power Mode by programming the CAN controller.
To disable Low-power Mode, the software application must:
– Enable the CAN Controller clock. This is done by programming the Power
Management Controller (PMC).
– Clear the LPM field in the CAN_MR register
The CAN controller synchronizes itself with the bus activity by checking for eleven consecutive
“recessive” bits. Once synchronized, the WAKEUP signal in the CAN_SR register is set.
SLEEP
(CAN_SR)
MRDY
(CAN_MSR1)
LPM
(CAN_MR)
LPEN= 1
CAN BUS
MRDY
(CAN_MSR3)
Mailbox 1
Mailbox 3
Arbitration lost
WAKEUP
(CAN_SR)
0x0
CAN_TIM
Содержание SAM9X25
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