Sleep mode is entered from the configuration mode when the following conditions are met.
1.Select sleep mode. Write a 1 to can.MSR[SLEEP] and write a 0 to can.MSR[LBACK].
2.Enable the controller. Write a 1 to can.SSR[CEN].
3.Wait for the TXFIFO or TXHPB to empty.
In configuration mode, can.MSR[SNOOP] = don't care.
Sleep mode is exited when I/O bus activity is detected or when software writes a message to either the TXFIFO or the TXHPB. When the controller exits sleep mode, can.MSR[SLEEP] is set to 0 and an interrupt is generated by the controller.