PM0223 datasheet(87/110 Pages) STMICROELECTRONICS

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PM0223

STM32L0 Core Peripherals

108

For a level-sensitive interrupt, if the interrupt signal is still asserted, the state of the interrupt

does not change. Otherwise, the state of the interrupt changes to inactive.

For a pulse interrupt, state of the interrupt changes to:

–

Inactive, if the state was pending.

–

Active, if the state was active and pending.

4.2.8

NVIC usage hints and tips

Ensure software uses correctly aligned register accesses. The processor does not support

unaligned accesses to NVIC registers.

An interrupt can enter pending state even if it is disabled. Disabling an interrupt only

prevents the processor from taking that interrupt.

Before programming VTOR to relocate the vector table, ensure the vector table entries of

the new vector table are set up for fault handlers, NMI and all enabled exception like

interrupts. For more information, see 4.3.4: Vector Table Offset Register on page 91.

NVIC programming hints

Software uses the CPSIE i and CPSIDi instructions to enable and disable interrupts. The

CMSIS provides the following intrinsic functions for these instructions:

void __disable_irq(void) // Disable Interrupts

void __enable_irq(void)

// Enable Interrupts

In addition, the CMSIS provides a number of functions for NVIC control, including:

The input parameter IRQn is the IRQ number, see Table 13 on page 27 for more information.

For more information about these functions, see the CMSIS documentation.

Table 29. CMSIS functions for NVIC control

CMSIS interrupt control function

Description

void NVIC_EnableIRQ(IRQn_t IRQn)

Enable IRQn.

void NVIC_DisableIRQ(IRQn_t IRQn)

Disable IRQn

uint32_t NVIC_GetPendingIRQ (IRQn_t IRQn)

Return true (1) if IRQn is

pending.

void NVIC_SetPendingIRQ (IRQn_t IRQn)

Set IRQn pending.

void NVIC_ClearPendingIRQ (IRQn_t IRQn)

Clear IRQn pending status.

void NVIC_SetPriority (IRQn_t IRQn,

uint32_t priority)

Set priority for IRQn.

uint32_t NVIC_GetPriority (IRQn_t IRQn)

Read priority of IRQn.

void NVIC_SystemReset (void)

Reset the system.

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