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In computing, a non-maskable interrupt (NMI) is a hardware interrupt that standard interrupt-masking techniques in the system cannot ignore. It typically occurs to signal attention for non-recoverable hardware errors. Some NMIs may be masked, but only by using proprietary methods specific to the particular NMI.
A hardware interrupt is a condition related to the state of the hardware that may be signaled by an external hardware device, e.g., an interrupt request (IRQ) line on a PC, or detected by devices embedded in processor logic (e.g., the CPU timer in IBM System/370), to communicate that the device needs attention from the operating system (OS) [7] or, if there is no OS, from the bare metal ...
The LPC1100(X)L-series consists of three subseries: LPC111x, LPC111xL, and LPC111xXL. The LPC111xL and LPC111xXL include the power profiles, a windowed watchdog timer, and a configurable open-drain mode. The LPC1110XL adds a Non-Maskable Interrupt (NMI) and 256-byte page flash erase function.
The detection of an NMI or IRQ signal, as well as the execution of a BRK instruction, will cause the same overall sequence of events, which are, in order: [1] [3]. The processor completes the current instruction and updates registers or memory as required before responding to the interrupt.
The IRR specifies which interrupts are pending acknowledgement, and is typically a symbolic register which can not be directly accessed. The ISR register specifies which interrupts have been acknowledged, but are still waiting for an end of interrupt (EOI). The IMR specifies which interrupts are to be ignored and not acknowledged.
Interrupt rate limiting must be carefully configured for optimum results. For example, an Ethernet controller with interrupt rate limiting will buffer the packets it receives from the network in between each interrupt. If the rate is set too low, the controller's buffer will overflow, and packets will be dropped.
An end of interrupt (EOI) is a computing signal sent to a programmable interrupt controller (PIC) to indicate the completion of interrupt processing for a given interrupt. Interrupts are used to facilitate hardware signals sent to the processor that temporarily stop a running program and allow a special program, an interrupt handler, to run ...
The interrupt priority level (IPL) is a part of the current system interrupt state, which indicates the interrupt requests that will currently be accepted. The IPL may be indicated in hardware by the registers in a programmable interrupt controller , or in software by a bitmask or integer value and source code of threads.