Functional Operation
9-38
ADSP-BF537 Blackfin Processor Hardware Reference
The suspend mode can subsequently be exited by clearing the
CSR
bit in
CAN_CONTROL
. The only differences between suspend mode and configura-
tion mode are that writes to the
CAN_CLOCK
and
CAN_TIMING
registers are
still locked in suspend mode and the CAN control and status registers are
not reset when exiting suspend mode.
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 (
SMR
) bit in the
CAN_CONTROL
register. The module enters the sleep
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 (
SMACK
)
bit is set in
CAN_INTR
. When the CAN module is in sleep mode, all register
reads return the contents of
CAN_INTR
instead of the usual contents. All
register writes, except to
CAN_INTR
, are ignored in sleep mode.
A small part of the module is clocked continuously to allow for wakeup
out of sleep mode. A write to the
CAN_INTR
register ends sleep mode. If the
WBA
bit in the
CAN_CONTROL
register is set before entering sleep mode, a
dominant bit on the
CANRX
pin also ends sleep mode.
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
μ
A) is that used by the regu-
lator 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
Summary of Contents for Blackfin ADSP-BF537
Page 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Page 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...