BAT32G1x9 user manual | Chapter 22 CAN control
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Rev.1.02
22.11.3
Example of power saving mode
In some application systems, it may be necessary to put the CPU into power-saving mode to reduce
power consumption. By using a power-down mode specific to the CAN module and a CPU-specific power-
down mode, the CAN bus can wake up the CPU from the power-down state.
Below is an example of using power saving mode
First, put the CAN module into CAN sleep mode (PSMODE=01B). Next, put the CPU into power
saving mode. If the CAN receive pin (CRxD) in this state detects edge transition from recessive to
dominant, the CINTS5 bit in the CAN module is set to 1. If the CIE5 bit of the CnCTRL register is set to 1, a
wake-up interrupt (INTCnWUP) is generated. The CAN module is automatically released from CAN sleep
mode (PSMODE=00B) and returns to normal operating mode (however, in the state where a CAN clock is
provided, the PSMODE0 bit needs to be cleared by software after the CAN receive pin (CRxD) detects a
bus change.) The CPU responds to INTCnWUP and can release its own power saving mode and return to
normal operation mode. .
To further reduce the CPU's power consumption, the internal clock (including the clock of the CAN
module) may stop. In this case, after the CAN module is placed in CAN sleep mode, the operating clock
provided to the CAN module will stop. The CPU then enters a power-down mode where the clock provided
to the CPU stops. If the CAN receive pin (CRxD) in this state detects edge transitions from recessive to
dominant, the CAN module can set the CINTS5 bit to 1 and generate a wake-up interrupt (INTCnWUP),
even if no clock is provided. However, the other features no longer work because the clock supply for the
CAN module has stopped and the module remains in CAN sleep mode. The CPU responds to INTCnWUP,
releases its power-down mode, restores power to the internal clock (including supplying the clock to the
CAN module) after the oscillation settling time has elapsed, and begins executing instructions. As soon as
the clock power is restored, the CAN module is released from CAN sleep mode and returns to normal
operating mode (PSMODE=00B).