Atmel Evaluation Kit AT91SAM9X25-EK AT91SAM9X25-EK データシート

909

SAM9X25 [DATASHEET]

11054E–ATARM–10-Mar-2014

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 

).

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