Exti Functional Behavior; Table 95. Masking Functionality; Figure 56. Direct Event Trigger Logic Cpu Wakeup - ST STM32WL5 Series Reference Manual

Extended interrupts and event controller (EXTI)
The direct events do not have an associated EXTI interrupt. The EXTI only wakes up the
system and CPU sub-system clocks and may generate a CPU wakeup event. The
peripheral synchronous interrupt associated with the direct wakeup event, wake up the
CPU. The EXTI direct event is able to generate a CPU event. This CPU event wakes up the
CPU.
The CPU event may occur before the associated peripheral interrupt flag is set.
AHB
interface
hclk
hclk
Asynchronous
Direct event
rising edge
input(x)
detect circuit
rst
EXTI
Logic duplicated for each CPU
16.5

EXTI functional behavior

The direct event inputs are enabled in the respective peripheral generating the wakeup
event. The configurable events are enabled by enabling at least one of the trigger edges.
Once an event input is enabled, the generation of a CPU wakeup is conditioned by the CPU
interrupt mask and the CPU event mask.
CPU interrupt enable
EXTI_CnIMRm.IMb
0
1
1. The single it_exti_per(y) interrupt goes to both CPUs. If no interrupt is required for the CPUn, the it_exti_per(y) interrupt
must be masked in the CPUn NVIC.
2. Only if the CPU interrupt is enabled in EXTI_CnIMRm.IMb.
For configurable event inputs, when the enabled edges occur on the event input, an event
request is generated. When the associated it_exti_per(y) interrupt is unmasked, the
corresponding pending bit in EXTI_PR is set, the CPU sub-system wakes up and the CPU
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Figure 56. Direct event trigger logic CPU wakeup

Peripheral interface
CPUn CPUn
interrupt event
mask register mask register
Falling edge
detect pulse
generator
hclk
1) Only for the input events supporting the CPUn rxrev generation cn_event.

Table 95. Masking functionality

CPU event enable
EXTI_CnEMRm.EMb
0
1
0
1
Same circuit for configurable
and direct events
(1)
CPUn event(x)
Rising edge
CPUn
other events(x,y)
CPUn wakeup(x)
CPUn other wakeups
Other wakeups
Wakeup(x)
Configurable
event inputs it_exti_per(y)
EXTI_PRm.PIFb
No
No
Status latched
Status latched
RM0453 Rev 1
EVG
hclk
cn_evt_rst
rising edge
detect cn_evt_exti
detect pulse
rst
hclk
cn_wakeup
sys_wakeup
(1)
CPUn event
Masked Masked
Masked Yes
Yes Masked
Yes Yes
RM0453
ck_fclk_cn
CPUn
cn_event
generator
MSv60762V1
CPUn
wakeup
Masked
Yes
(2)
Yes
Yes