Can Built-In Sleep Mode; Can Wakeup From Hibernate State - Analog Devices ADSP-BF506F Hardware Reference Manual

Functional Operation

CAN Built-In Sleep Mode

The next level of power savings can be realized by using the CAN mod-
ule's built-in sleep mode. This mode is entered by setting the sleep mode
request ( ) bit in the
SMR
mode after the current operation of the CAN bus is finished. Once this
mode is entered, many of the internal CAN module clocks are shut off,
reducing power consumption, and the sleep mode acknowledge (
bit is set in
CAN_INTR
reads return the contents of
register writes, except to
A small part of the module is clocked continuously to allow for wakeup
out of sleep mode. A write to the
bit in the
WBA CAN_CONTROL
dominant bit on the

CAN Wakeup From Hibernate State

For greatest power savings, the Blackfin processor provides a hibernate
state, where the internal voltage regulator shuts off the internal power sup-
ply to the chip, turning off the core and system clocks in the process. In
this mode, the only power drawn (roughly 50
regulator circuitry awaiting any of the possible hibernate wakeup events.
One such event is a wakeup due to CAN bus activity. After hibernation,
the CAN module must be re-initialized.
For low power designs, the external CAN bus transceiver is typically put
into standby mode via one of the Blackfin processor's general purpose I/O
pins. While in standby mode, the CAN transceiver continually drives the
recessive logic '1' level onto the
CAN bus activity, it will, in turn, drive the
logic '0' level. This signals to the Blackfin processor that CAN bus activity
has been detected. If the internal voltage regulator is programmed to
recognize CAN bus activity as an event to exit hibernate state, the part
17-38
register. The module enters the sleep
CAN_CONTROL
. When the CAN module is in sleep mode, all register
instead of the usual contents. All
CAN_INTR
, are ignored in sleep mode.
CAN_INTR
CAN_INTR
register is set before entering sleep mode, a
pin also ends sleep mode.
CANRX
CANRX
ADSP-BF50x Blackfin Processor Hardware Reference
register ends sleep mode. If the

A) is that used by the
pin. If the transceiver then senses
pin to the dominant
CANRX
)
SMACK