CMSIS-Core (Cortex-M)  Version 5.1.0
CMSIS-Core support for Cortex-M processor-based devices
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Interrupts and Exceptions (NVIC)

Functions to access the Nested Vector Interrupt Controller (NVIC). More...

Macros

#define CMSIS_NVIC_VIRTUAL
 Virtualization of the NVIC API. More...
 
#define CMSIS_VECTAB_VIRTUAL
 Virtualization of interrupt vector table access functions. More...
 

Enumerations

enum  IRQn_Type {
  NonMaskableInt_IRQn = -14,
  HardFault_IRQn = -13,
  MemoryManagement_IRQn = -12,
  BusFault_IRQn = -11,
  UsageFault_IRQn = -10,
  SecureFault_IRQn = -9,
  SVCall_IRQn = -5,
  DebugMonitor_IRQn = -4,
  PendSV_IRQn = -2,
  SysTick_IRQn = -1,
  WWDG_STM_IRQn = 0,
  PVD_STM_IRQn = 1
}
 Definition of IRQn numbers. More...
 

Functions

void NVIC_SetPriorityGrouping (uint32_t PriorityGroup)
 Set priority grouping [not for Cortex-M0, Cortex-M0+, or SC000]. More...
 
uint32_t NVIC_GetPriorityGrouping (void)
 Read the priority grouping [not for Cortex-M0, Cortex-M0+, or SC000]. More...
 
void NVIC_EnableIRQ (IRQn_Type IRQn)
 Enable a device specific interrupt. More...
 
uint32_t NVIC_GetEnableIRQ (IRQn_Type IRQn)
 Get a device specific interrupt enable status. More...
 
void NVIC_DisableIRQ (IRQn_Type IRQn)
 Disable a device specific interrupt. More...
 
uint32_t NVIC_GetPendingIRQ (IRQn_Type IRQn)
 Get the pending device specific interrupt. More...
 
void NVIC_SetPendingIRQ (IRQn_Type IRQn)
 Set a device specific interrupt to pending. More...
 
void NVIC_ClearPendingIRQ (IRQn_Type IRQn)
 Clear a device specific interrupt from pending. More...
 
uint32_t NVIC_GetActive (IRQn_Type IRQn)
 Get the device specific interrupt active status [not for Cortex-M0, Cortex-M0+, or SC000]. More...
 
void NVIC_SetPriority (IRQn_Type IRQn, uint32_t priority)
 Set the priority for an interrupt. More...
 
uint32_t NVIC_GetPriority (IRQn_Type IRQn)
 Get the priority of an interrupt. More...
 
uint32_t NVIC_EncodePriority (uint32_t PriorityGroup, uint32_t PreemptPriority, uint32_t SubPriority)
 Encodes Priority [not for Cortex-M0, Cortex-M0+, or SC000]. More...
 
void NVIC_DecodePriority (uint32_t Priority, uint32_t PriorityGroup, uint32_t *pPreemptPriority, uint32_t *pSubPriority)
 Decode the interrupt priority [not for Cortex-M0, Cortex-M0+, or SC000]. More...
 
uint32_t NVIC_GetVector (IRQn_Type IRQn)
 Read Interrupt Vector [not for Cortex-M0, SC000]. More...
 
void NVIC_SetVector (IRQn_Type IRQn, uint32_t vector)
 Modify Interrupt Vector [not for Cortex-M0, SC000]. More...
 
void NVIC_SystemReset (void)
 Reset the system. More...
 
uint32_t NVIC_GetTargetState (IRQn_Type IRQn)
 Get Interrupt Target State. More...
 
uint32_t NVIC_SetTargetState (IRQn_Type IRQn)
 Set Interrupt Target State. More...
 
uint32_t NVIC_ClearTargetState (IRQn_Type IRQn)
 Clear Interrupt Target State. More...
 

Description

This section explains how to use interrupts and exceptions and access functions for the Nested Vector Interrupt Controller (NVIC).

ARM provides a template file startup_device for each supported compiler. The file must be adapted by the silicon vendor to include interrupt vectors for all device-specific interrupt handlers. Each interrupt handler is defined as a weak function to an dummy handler. These interrupt handlers can be used directly in application software without being adapted by the programmer.

The table below lists the core exception vectors of the various Cortex-M processors.

Exception Vector IRQn
Value
M0 M0+ M3 M4 M7 SC000 SC300 ARMv8-M
Baseline
ARMv8-M
Mainline
Description
NonMaskableInt_IRQn -14
available
available
available
available
available
available
available
available
available
Non Maskable Interrupt
HardFault_IRQn -13
available
available
available
available
available
available
available
available
available
Hard Fault Interrupt
MemoryManagement_IRQn -12    
available
available
available
 
available
 
available
Memory Management Interrupt
BusFault_IRQn -11    
available
available
available
 
available
 
available
Bus Fault Interrupt
UsageFault_IRQn -10    
available
available
available
 
available
 
available
Usage Fault Interrupt
SecureFault_IRQn -9              
available
available
Secure Fault Interrupt
SVCall_IRQn -5
available
available
available
available
available
available
available
available
available
SV Call Interrupt
DebugMonitor_IRQn -4    
available
available
available
 
available
 
available
Debug Monitor Interrupt
PendSV_IRQn -2
available
available
available
available
available
available
available
available
available
Pend SV Interrupt
SysTick_IRQn -1
available
available
available
available
available
available
available
available
available
System Tick Interrupt

Vector Table

The Vector Table defines the entry addresses of the processor exceptions and the device specific interrupts. It is typically located at the beginning of the program memory, however Using Interrupt Vector Remap it can be relocated to RAM. The symbol __Vectors is the address of the vector table in the startup code and the register SCB->VTOR holds the start address of the vector table.

An ARMv8-M implementation with TrustZone provides two vector tables:

Refer to Programmers Model with TrustZone for more information.

Processor Exceptions

At the beginning of the vector table, the initial stack value and the exception vectors of the processor are defined. The vector table below shows the exception vectors of a ARMv8-M Mainline processor. Other processor variants may have fewer vectors.

__Vectors DCD __initial_sp ; Top of Stack initialization
DCD Reset_Handler ; Reset Handler
DCD NMI_Handler ; NMI Handler
DCD HardFault_Handler ; Hard Fault Handler
DCD MemManage_Handler ; MPU Fault Handler
DCD BusFault_Handler ; Bus Fault Handler
DCD UsageFault_Handler ; Usage Fault Handler
DCD SecureFault_Handler ; Secure Fault Handler
DCD 0 ; Reserved
DCD 0 ; Reserved
DCD 0 ; Reserved
DCD SVC_Handler ; SVCall Handler
DCD DebugMon_Handler ; Debug Monitor Handler
DCD 0 ; Reserved
DCD PendSV_Handler ; PendSV Handler
DCD SysTick_Handler ; SysTick Handler

Device Specific Vectors

Following the processor exception vectors, the vector table contains also the device specific interrupt vectors.

; device specific interrupts
DCD WWDG_IRQHandler ; Window Watchdog
DCD PVD_IRQHandler ; PVD through EXTI Line detect
DCD TAMPER_IRQHandler ; Tamper

All device specific interrupts should have a default interrupt handler function that can be overwritten in user code. Below is an example for this default handler function.

Default_Handler PROC
EXPORT WWDG_IRQHandler [WEAK]
EXPORT PVD_IRQHandler [WEAK]
EXPORT TAMPER_IRQHandler [WEAK]
:
:
WWDG_IRQHandler
PVD_IRQHandler
TAMPER_IRQHandler
:
:
B .
ENDP

The user application may simply define an interrupt handler function by using the handler name as shown below.

void WWDG_IRQHandler(void)
{
...
}

NVIC Function Usage

The code below shows the usage of various CMSIS NVIC functions with an LPC1700 device.

Code Example 1

#include "LPC17xx.h"
uint32_t priorityGroup; /* Variables to store priority group and priority */
uint32_t priority;
uint32_t preemptPriority;
uint32_t subPriority;
int main (void) {
NVIC_SetPriorityGrouping(5); /* Set priority group to 5:
Bit[7..6] preempt priority Bits,
Bit[5..3] subpriority Bits
(valid for five priority bits) */
priorityGroup = NVIC_GetPriorityGrouping(); /* Get used priority grouping */
priority = NVIC_EncodePriority(priorityGroup, 1, 6); /* Encode priority with 6 for subpriority and 1 for preempt priority
Note: priority depends on the used priority grouping */
NVIC_SetPriority(UART0_IRQn, priority); /* Set new priority */
priority = NVIC_GetPriority(UART0_IRQn); /* Retrieve priority again */
NVIC_DecodePriority(priority, priorityGroup, &preemptPriority, &subPriority);
while(1);
}

Code Example 2

#include "LPC17xx.h"
uint32_t active; /* Variable to store interrupt active state */
void TIMER0_IRQHandler(void) { /* Timer 0 interrupt handler */
if (LPC_TIM0->IR & (1 << 0)) { /* Check if interrupt for match channel 0 occured */
LPC_TIM0->IR |= (1 << 0); /* Acknowledge interrupt for match channel 0 occured */
}
active = NVIC_GetActive(TIMER0_IRQn); /* Get interrupt active state of timer 0 */
}
int main (void) {
/* Set match channel register MR0 to 1 millisecond */
LPC_TIM0->MR0 = (((SystemCoreClock / 1000) / 4) - 1); /* 1 ms? */
LPC_TIM0->MCR = (3 << 0); /* Enable interrupt and reset for match channel MR0 */
NVIC_EnableIRQ(TIMER0_IRQn); /* Enable NVIC interrupt for timer 0 */
LPC_TIM0->TCR = (1 << 0); /* Enable timer 0 */
while(1);
}

NVIC API Virtualization

The CMSIS-Core has provisions for overriding NVIC APIs as required for implementing secure systems that control access to peripherals and related interrupts. These overrides allow an operating system to control the access privileges of application code to critical interrupts.

The NVIC function virtualization is enabled with the following #define symbols:

Macro Definition Documentation

#define CMSIS_NVIC_VIRTUAL

When CMSIS_NVIC_VIRTUAL is defined, the NVIC access functions in the table below must be implemented for virtualizing NVIC access. These functions should be implemented in a separate source module. The original CMSIS-Core __NVIC functions are always available independent of CMSIS_NVIC_VIRTUAL.

NVIC Access Functions CMSIS-Core Functions
NVIC_EnableIRQ __NVIC_EnableIRQ
NVIC_GetEnableIRQ __NVIC_GetEnableIRQ
NVIC_DisableIRQ __NVIC_DisableIRQ
NVIC_GetPendingIRQ __NVIC_GetPendingIRQ
NVIC_SetPendingIRQ __NVIC_SetPendingIRQ
NVIC_ClearPendingIRQ __NVIC_ClearPendingIRQ
NVIC_GetActive __NVIC_GetActive
NVIC_SetPriority __NVIC_SetPriority
NVIC_GetPriority __NVIC_GetPriority
NVIC_SetPriorityGrouping __NVIC_SetPriorityGrouping
NVIC_GetPriorityGrouping __NVIC_GetPriorityGrouping
#define CMSIS_VECTAB_VIRTUAL

When CMSIS_NVIC_VIRTUAL is defined, the functions in the table below must be replaced to virtualize the API access functions to the interrupt vector table. The NVIC vector table API should be implemented in a separate source module. This allows, for example, alternate implementations to relocate the vector table from flash to RAM on the first vector table update.

The original CMSIS-Core functions are always available, but prefixed with __NVIC.

Interrupt Vector Table Access CMSIS-Core Functions
NVIC_GetVector __NVIC_GetVector
NVIC_SetVector __NVIC_SetVector

Enumeration Type Documentation

enum IRQn_Type

The core exception enumeration names for IRQn values are defined in the file device.h.

  • Negative IRQn values represent processor core exceptions (internal interrupts).
  • Positive IRQn values represent device-specific exceptions (external interrupts).
  • The first device-specific interrupt has the IRQn value 0.

The table below describes the core exception names and their availability in various Cortex-M cores.

Enumerator
NonMaskableInt_IRQn 

Exception 2: Non Maskable Interrupt.

HardFault_IRQn 

Exception 3: Hard Fault Interrupt.

MemoryManagement_IRQn 

Exception 4: Memory Management Interrupt [not on Cortex-M0 variants].

BusFault_IRQn 

Exception 5: Bus Fault Interrupt [not on Cortex-M0 variants].

UsageFault_IRQn 

Exception 6: Usage Fault Interrupt [not on Cortex-M0 variants].

SecureFault_IRQn 

Exception 7: Secure Fault Interrupt [only on ARMv8-M].

SVCall_IRQn 

Exception 11: SV Call Interrupt.

DebugMonitor_IRQn 

Exception 12: Debug Monitor Interrupt [not on Cortex-M0 variants].

PendSV_IRQn 

Exception 14: Pend SV Interrupt [not on Cortex-M0 variants].

SysTick_IRQn 

Exception 15: System Tick Interrupt.

WWDG_STM_IRQn 

Device Interrupt 0: Window WatchDog Interrupt.

PVD_STM_IRQn 

Device Interrupt 1: PVD through EXTI Line detection Interrupt.

Function Documentation

void NVIC_ClearPendingIRQ ( IRQn_Type  IRQn)

This function removes the pending state of the specified device specific interrupt IRQn. IRQn cannot be a negative number.

Parameters
[in]IRQnInterrupt number
Remarks
  • IRQn must not be negative.
  • The registers that control the status of interrupts are called SETPEND and CLRPEND.
  • An interrupt can have the status pending though it is not active.
See Also
uint32_t NVIC_ClearTargetState ( IRQn_Type  IRQn)

Clears the interrupt target field in the non-secure NVIC when in secure state.

Parameters
[in]IRQnExternal interrupt number. Value cannot be negative.
Returns
  • 0 if interrupt is assigned to Secure
  • 1 if interrupt is assigned to Non Secure
Remarks
  • Only available for ARMv8-M in secure state.
See Also
void NVIC_DecodePriority ( uint32_t  Priority,
uint32_t  PriorityGroup,
uint32_t *  pPreemptPriority,
uint32_t *  pSubPriority 
)

This function decodes an interrupt priority value with the priority group PriorityGroup to preemptive priority value pPreemptPriority and subpriority value pSubPriority. In case of a conflict between priority grouping and available priority bits (__NVIC_PRIO_BITS) the smallest possible priority group is set.

Parameters
[in]PriorityPriority
[in]PriorityGroupPriority group
[out]*pPreemptPriorityPreemptive priority value (starting from 0)
[out]*pSubPrioritySubpriority value (starting from 0)
Remarks
  • not for Cortex-M0, Cortex-M0+, or SC000.
See Also
void NVIC_DisableIRQ ( IRQn_Type  IRQn)

This function disables the specified device specific interrupt IRQn. IRQn cannot be a negative value.

Parameters
[in]IRQnNumber of the external interrupt to disable
Remarks
  • IRQn must not be negative.
  • The registers that control the enabling and disabling of interrupts are called SETENA and CLRENA.
See Also
void NVIC_EnableIRQ ( IRQn_Type  IRQn)

This function enables the specified device specific interrupt IRQn. IRQn cannot be a negative value.

Parameters
[in]IRQnInterrupt number
Remarks
  • IRQn must not be negative.
  • The registers that control the enabling and disabling of interrupts are called SETENA and CLRENA.
  • The number of supported interrupts depends on the implementation of the chip designer and can be read form the Interrupt Controller Type Register (ICTR) in granularities of 32:
    ICTR[4:0]
    • 0 - 32 interrupts supported
    • 1 - 64 interrupts supported
    • ...
See Also
uint32_t NVIC_EncodePriority ( uint32_t  PriorityGroup,
uint32_t  PreemptPriority,
uint32_t  SubPriority 
)

This function encodes the priority for an interrupt with the priority group PriorityGroup, preemptive priority value PreemptPriority, and subpriority value SubPriority. In case of a conflict between priority grouping and available priority bits (__NVIC_PRIO_BITS) the smallest possible priority group is set.

Parameters
[in]PriorityGroupPriority group
[in]PreemptPriorityPreemptive priority value (starting from 0)
[in]SubPrioritySubpriority value (starting from 0)
Returns
Encoded priority for the interrupt
Remarks
  • not for Cortex-M0, Cortex-M0+, or SC000.
See Also
uint32_t NVIC_GetActive ( IRQn_Type  IRQn)

This function reads the Interrupt Active Register (NVIC_IABR0-NVIC_IABR7) in NVIC and returns the active bit of the interrupt IRQn.

Parameters
[in]IRQnInterrupt number
Returns
  • 0 Interrupt is not active
  • 1 Interrupt is active, or active and pending
Remarks
  • not for Cortex-M0, Cortex-M0+, or SC000.
  • IRQn must not be negative.
  • Each external interrupt has an active status bit. When the processor starts the interrupt handler the bit is set to 1 and cleared when the interrupt return is executed.
  • When an ISR is preempted and the processor executes anohter interrupt handler, the previous interrupt is still defined as active.
See Also
uint32_t NVIC_GetEnableIRQ ( IRQn_Type  IRQn)

This function returns the interrupt enable status for the specified device specific interrupt IRQn. IRQn cannot be a negative value.

Parameters
[in]IRQnInterrupt number
Returns
  • 0 Interrupt is not enabled
  • 1 Interrupt is pending
Remarks
  • IRQn must not be negative.
  • The registers that control the enabling and disabling of interrupts are called SETENA and CLRENA.
See Also
uint32_t NVIC_GetPendingIRQ ( IRQn_Type  IRQn)

This function returns the pending status of the specified device specific interrupt IRQn.

Parameters
[in]IRQnInterrupt number
Returns
  • 0 Interrupt is not pending
  • 1 Interrupt is pending
Remarks
  • IRQn must not be negative.
  • The registers that control the status of interrupts are called SETPEND and CLRPEND.
See Also
uint32_t NVIC_GetPriority ( IRQn_Type  IRQn)

This function reads the priority for the specified interrupt IRQn. IRQn can can specify any device specific interrupt, or processor exception.

The returned priority value is automatically aligned to the implemented priority bits of the microcontroller.

Parameters
[in]IRQnInterrupt number
Returns
Interrupt priority
Remarks
  • Each external interrupt has an associated priority-level register.
  • Unimplemented bits are read as zero.
See Also
uint32_t NVIC_GetPriorityGrouping ( void  )

This function returns the priority grouping (flag PRIGROUP in AIRCR[10:8]).

Returns
Priority grouping field
Remarks
  • not for Cortex-M0, Cortex-M0+, or SC000.
  • By default, priority group setting is zero.
See Also
uint32_t NVIC_GetTargetState ( IRQn_Type  IRQn)

Reads the interrupt target field from the non-secure NVIC when in secure state.

Parameters
[in]IRQnExternal interrupt number. Value cannot be negative.
Returns
  • 0 if interrupt is assigned to Secure
  • 1 if interrupt is assigned to Non Secure
Remarks
  • Only available for ARMv8-M in secure state.
See Also
uint32_t NVIC_GetVector ( IRQn_Type  IRQn)

This function allows to read the address of an interrupt handler function.

Parameters
[in]IRQnInterrupt number
Returns
Address of interrupt handler function
Remarks
  • For using this function with Cortex-M0+ processor based devices, the SBC->VTOR register must be implemented.
See Also
void NVIC_SetPendingIRQ ( IRQn_Type  IRQn)

This function sets the pending bit for the specified device specific interrupt IRQn. IRQn cannot be a negative value.

Parameters
[in]IRQnInterrupt number
Remarks
  • IRQn must not be negative.
  • The registers that control the status of interrupts are called SETPEND and CLRPEND.
See Also
void NVIC_SetPriority ( IRQn_Type  IRQn,
uint32_t  priority 
)

Sets the priority for the interrupt specified by IRQn.IRQn can can specify any device specific interrupt, or processor exception. The priority specifies the interrupt priority value, whereby lower values indicate a higher priority. The default priority is 0 for every interrupt. This is the highest possible priority.

The priority cannot be set for every core interrupt. HardFault and NMI have a fixed (negative) priority that is higher than any configurable exception or interrupt.

Parameters
[in]IRQnInterrupt Number
[in]priorityPriority to set
Remarks
  • The number of priority levels is configurable and depends on the implementation of the chip designer. To determine the number of bits implemented for interrupt priority-level registers, write 0xFF to one of the priority-level register, then read back the value. For example, if the minimum number of 3 bits have been implemented, the read-back value is 0xE0.
  • Writes to unimplemented bits are ignored.
  • For Cortex-M0:
    • Dynamic switching of interrupt priority levels is not supported. The priority level of an interrupt should not be changed after it has been enabled.
    • Supports 0 to 192 priority levels.
    • Priority-level registers are 2 bit wide, occupying the two MSBs. Each Interrupt Priority Level Register is 1-byte wide.
  • For Cortex-M3, Cortex-M4, and Cortex-M7:
    • Dynamic switching of interrupt priority levels is supported.
    • Supports 0 to 255 priority levels.
    • Priority-level registers have a maximum width of 8 bits and a minumum of 3 bits. Each register can be further devided into preempt priority level and subpriority level.
See Also
void NVIC_SetPriorityGrouping ( uint32_t  PriorityGroup)

The function sets the priority grouping PriorityGroup using the required unlock sequence. PriorityGroup is assigned to the field PRIGROUP (register AIRCR[10:8]). This field determines the split of group priority from subpriority. Only values from 0..7 are used. In case of a conflict between priority grouping and available priority bits (__NVIC_PRIO_BITS), the smallest possible priority group is set.

Parameters
[in]PriorityGroupPriority group
Remarks
  • not for Cortex-M0, Cortex-M0+, or SC000.
  • By default, priority group setting is zero.
See Also
uint32_t NVIC_SetTargetState ( IRQn_Type  IRQn)

Sets the interrupt target field in the non-secure NVIC when in secure state.

Parameters
[in]IRQnExternal interrupt number. Value cannot be negative.
Returns
  • 0 if interrupt is assigned to Secure
  • 1 if interrupt is assigned to Non Secure
Remarks
  • Only available for ARMv8-M in secure state.
See Also
void NVIC_SetVector ( IRQn_Type  IRQn,
uint32_t  vector 
)

This function allows to change the address of an interrupt handler function.

Parameters
[in]IRQnInterrupt number
[in]vectorAddress of new interrupt handler function
Remarks
  • Usage of this function requires vector relocation to RAM. Refer to Using Interrupt Vector Remap for more information.
    • For using this function with Cortex-M0+ processor based devices, the SBC->VTOR register must be implemented.
See Also
void NVIC_SystemReset ( void  )

This function requests a system reset by setting the SYSRESETREQ flag in the AIRCR register.

Remarks
  • In most microcontroller designs, setting the SYSRESETREQ flag resets the processor and most parts of the system, but should not affect the debug system.
See Also