Datasheet

880
SAM9X35 [DATASHEET]
11055E–ATARM–10-Mar-2014
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 important 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 Management 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.
Depending on the corresponding mask in the CAN_IMR register, an interrupt is generated while WAKEUP is set. The
SLEEP signal in the CAN_SR register is automatically cleared once WAKEUP is set. WAKEUP signal is automatically
cleared once SLEEP is set.
If no message is being sent on the bus, then the CAN controller is able to send a message eleven bit times after disabling
Low-power Mode.
If there is bus activity when Low-power mode is disabled, the CAN controller is synchronized with the bus activity in the
next interframe. The previous message is lost (see Figure 41-9).
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)
0x0CAN_TIM