SAM7X128_14 Datasheet, PDF (494/662 Pages) ATMEL Corporation – ARM-based Flash MCU

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 36-8. Enabling Low-power Mode
Arbitration lost
CAN BUS
LPEN= 1
LPM
(CAN_MR)
SLEEP
(CAN_SR)
WAKEUP
(CAN_SR)
MRDY
(CAN_MSR1)
MRDY
(CAN_MSR3)
CAN_TIM
Mailbox 1
Mailbox 3
0x0
36.6.5.2 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 36-9).
SAM7X Series [DATASHEET]
6120K–ATARM–11-Feb-14
494