Fast interrupt request

Fast interrupt request (FIQ) is a specialized type of <a href="/facts/Interrupt_request/n2VvmL4K">interrupt request</a>, which is a standard technique used in computer CPUs to deal with events that need to be processed as they occur, such as receiving data from a network card, or keyboard or mouse actions. FIQs are specific to the <a href="/facts/ARM_architecture/SALsYA79">ARM architecture</a>, which supports two types of interrupts; FIQs for fast, low-latency interrupt handling, and standard interrupt requests (IRQs), for more general interrupts.
An FIQ takes priority over an IRQ in an ARM system. Only one FIQ source at a time is supported. This helps reduce interrupt latency as the interrupt service routine can be executed directly without determining the source of the interrupt. A context save is not required for servicing an FIQ since it has its own set of banked registers. This reduces the overhead of <a href="/facts/Context_switch/N0oJQ6CC">context switching</a>.
FIQs are often used for data transfers such as <a href="/facts/Direct_memory_access/DWuVgclV">direct memory access</a> operations.
FIQs can be disabled by clearing the F bit in the CPSR (Current Program Status Register).

Fast interrupt request open-in-new

Fast interrupt request