Figure 24. Cpu2 Boot Options - ST STM32WL5 Series Reference Manual

RM0453
When CPU1 is used to initialize the system before CPU2 is booted, the procedure is the
following:
•
Before CPU1 enters CStop mode, it clears the C2BOOT bit.
•
When CPU1 exits CStop:
–
–
–

Figure 24. CPU2 boot options

Reset
1
CPU1 CRUN, CSLEEP,
CPU2 CSTOP (BOOT HOLD)
5
CPU1 CRUN or CSLEEP
CPU2 CSTOP (BOOT HOLD)
7
CPU1 CSTOP
CPU2 CSTOP (BOOT HOLD)
9
STANDBY
CPU2 CSTOP (BOOT HOLD)
The system remains in Run mode and sets the C2BOOT bit, subsequently
processing the wakeup event.
The system exits a low-power mode from a CPU1 wakeup source. This initializes
the system and sets the C2BOOT bit, subsequently processing the wakeup event.
The system exits a low-power mode from a CPU2 wakeup source. The C2HF
wakeup source wakes up CPU1, that initializes the system and sets the C2BOOT
bit.CPU1 subsequently goes back to CStop. After C2BOOT is set, CPU2 is woken
up by its wakeup source.
ILAC handling
CPU2 CSTOP
6
CPU1 CRUN, CSLEEP,
CPU2 CRUN, CSLEEP
C2BOOTS = 0
(ILAC)
2
C2BOOT = 1
and
(C2BOOTS = 1)
3
CPU1 CRUN or CSLEEP
CPU2 CSTOP
CPU1 CSTOP
Wake up CPU1
and
C2BOOT = 0
8
10
STANDBY
RM0453 Rev 1
Power control (PWR)
CPU1 CRUN or CSLEEP
CPU2 CRUN or CSLEEP
4
CPU1 CSTOP
CPU2 CRUN or CSLEEP
CPU1 CSTOP
CPU2 CSTOP
Enter STANDBY
STANDBY
Wake up CPU2 and C2BOOT = 1
RUN
LP-RUN
STOP0
STOP1
STOP2
LP_STOP
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