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Chapter 18
18.11.3 Example of using power saving modes
622
In some application systems, it may be necessary to place the CPU in a power
saving mode to reduce the power consumption. By using the power saving
mode specific to the CAN module and the power saving mode specific to the
CPU in combination, the CPU can be woken up from the power saving status
by the CAN bus.
Here is an example for using the power saving modes.
• First, put the CAN module in the CAN sleep mode (PSMODE[1:0] = 01
Next, put the CPU in the power saving mode. If an edge transition from
recessive to dominant is detected at the CAN reception pin (CRXDn) in this
status, the CINTS5 bit in the CAN module is set to 1. If the CIE5 bit of the
CnCTRL register is set to 1, a wakeup interrupt (INTWUPn) is generated.
• The CAN module is automatically released from CAN sleep mode
(PSMODE = 00
) and returns to normal operation mode.
B
• The CPU, in response to INTWUPn, can release its own power saving mode
and return to normal operation mode.
To further reduce the power consumption of the CPU, the internal clock
- including that of the CAN module - may be stopped. In this case, the
operating clock supplied to the CAN module is stopped after the CAN
module has been put in CAN sleep mode. Then the CPU enters a power
saving mode in which the clock supplied to the CPU is stopped.
• If an edge transition from recessive to dominant is detected at the CAN
reception pin (CRXDn) in this status, the CAN module can set the CINTS5
bit to 1 and generate the wakeup interrupt (INTWUPn) even if it is not
supplied with the clock.
• The other functions, however, do not operate, because clock supply to the
CAN module is stopped, and the module remains in CAN sleep mode.
• The CPU, in response to INTWUPn
– releases its power saving mode,
– resumes supply of the internal clocks - including the clock to the CAN
module - after the oscillation stabilization time has elapsed, and
– starts instruction execution.
• The CAN module is immediately released from the CAN sleep mode when
clock supply is resumed, and returns to the normal operation mode
(PSMODE = 00
).
B
User's Manual U18743EE1V2UM00
CAN Controller (CAN)
).
B
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