Struct cortex_m::peripheral::nvic::RegisterBlock

#[repr(C)]pub struct RegisterBlock {
    pub iser: [RW<u32>; 16],
    pub icer: [RW<u32>; 16],
    pub ispr: [RW<u32>; 16],
    pub icpr: [RW<u32>; 16],
    pub iabr: [RO<u32>; 16],
    pub ipr: [RW<u8>; 496],
    // some fields omitted
}

Register block

Fields

iser: [RW<u32>; 16]

Interrupt Set-Enable

icer: [RW<u32>; 16]

Interrupt Clear-Enable

ispr: [RW<u32>; 16]

Interrupt Set-Pending

icpr: [RW<u32>; 16]

Interrupt Clear-Pending

iabr: [RO<u32>; 16]

Interrupt Active Bit (not present on Cortex-M0 variants)

ipr: [RW<u8>; 496]

Interrupt Priority

On ARMv7-M, 124 word-sized registers are available. Each of those contains of 4 interrupt priorities of 8 byte each.The architecture specifically allows accessing those along byte boundaries, so they are represented as 496 byte-sized registers, for convenience, and to allow atomic priority updates.

On ARMv6-M, the registers must only be accessed along word boundaries, so convenient byte-sized representation wouldn't work on that architecture.