Datasheet

163
11011B–ATARM–21-Feb-12
SAM3N
10.20.10 NVIC design hints and tips
Ensure software uses correctly aligned register accesses. The processor does not support
unaligned accesses to NVIC registers. See the individual register descriptions for the supported
access sizes.
A interrupt can enter pending state even it is disabled.
Before programming VTOR to relocate the vector table, ensure the vector table entries of the
new vector table are setup for fault handlers and all enabled exception like interrupts. For more
information see “Vector Table Offset Register” on page 170.
10.20.10.1 NVIC programming hints
Software uses the CPSIE I and CPSID I 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:
For more information about these functions see the CMSIS documentation.
Table 10-29. CMSIS functions for NVIC control
CMSIS interrupt control function Description
void NVIC_SetPriorityGrouping(uint32_t
priority_grouping)
Set the priority grouping
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 if IRQn is pending
void NVIC_SetPendingIRQ (IRQn_t IRQn) Set IRQn pending
void NVIC_ClearPendingIRQ (IRQn_t IRQn) Clear IRQn pending status
uint32_t NVIC_GetActive (IRQn_t IRQn)
Return the IRQ number of the active
interrupt
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