Programmable interrupt controller: Difference between revisions

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{{Short description|Integrated circuit that handles interrupts}}

{{distinguish| PIC microcontroller }}

{{Multiple issues|

{{one source|date=February 2014}}

{{nomore footnotes|date=September 2013}}

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In [[computing]], a '''programmable interrupt controller''' ('''PIC''') is a device that helps [[microprocessor]] (or [[CPU]]) to handle [[Interrupt request (PC architecture)|interrupt requests]] (IRQ) coming from multiple different sources (like external I/O devices) which may come (get fired) simultaneously.<ref>{{Cite web|title=Interrupt Controller - an overview {{!}} ScienceDirect Topics|url=https://www.sciencedirect.com/topics/engineering/interrupt-controller|access-date=2020-07-26|website=www.sciencedirect.com}}</ref> It helps to prioritize IRQs so that CPU switches to the most appropriate [[interrupt handler]] (ISR) after PIC assertes IRQ's relative priority. Common modes of a PIC include hard priorities, rotating priorities, and cascading priorities.{{Citation needed|date=July 2011}} PICs often allow the cascading of their outputs to inputs between each other. On [[PC architecture]] PIC are typically ebedded into a [[Southbridge (computing)|southbridge chips]] whose internal architecture is defined by chipsets' vendors' standards.

In [[computing]], a '''programmable interrupt controller''' ('''PIC''') is an [[integrated circuit]] that helps a [[microprocessor]] (or [[CPU]]) handle [[Interrupt request (PC architecture)|interrupt requests]] (IRQs) coming from multiple different sources (like external I/O devices) which may occur simultaneously.<ref>{{cite journal|title=A Revisitation of Kernel Synchronization Schemes

|author1=Christopher Small |author2=Stephen Manley

In [[computing]], a '''programmable interrupt controller''' ('''PIC''') is a device that helps [[microprocessor]] (or [[CPU]]) to handle [[Interrupt request (PC architecture)|interrupt requests]] (IRQ) coming from multiple different sources (like external I/O devices) which may come (get fired) simultaneously.<ref>{{Cite web|title=Interrupt Controller - an overview {{!}} ScienceDirect Topics|url=https://wwwstatic.sciencedirectusenix.comorg/topicspublications/engineeringlibrary/interrupt-controller|access-date=2020-07-26|website=www.sciencedirectproceedings/ana97/full_papers/small/small.comhtml}}</ref> It helps to prioritize IRQs so that the CPU switches execution to the most appropriate [[interrupt handler]] (ISR) after the PIC assertesassesses IRQthe IRQs's relative prioritypriorities. Common modes of ainterrupt PICpriority include hard priorities, rotating priorities, and cascading priorities.{{Citation needed|date=July 2011}} PICs often allow themapping cascadinginput of theirto outputs toin inputsa betweenconfigurable each otherway. On the [[PC architecture]] PIC are typically ebeddedembedded into a [[Southbridge (computing)|southbridge chipschip]] whose internal architecture is defined by chipsets'the vendorschipset vendor's standards.

==Common features==

PICs typically have a common set of registers: Interruptinterrupt Requestrequest Registerregister (IRR), Inin-Serviceservice Registerregister (ISR), Interruptand Maskinterrupt Registermask register (IMR). 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 [[Endend of interrupt|End Of Interrupt]] (EOI). The IMR specifies which interrupts are to be ignored and not acknowledged. A simple register schema such as this allows up to two distinct interrupt requests to be outstanding at one time, one waiting for acknowledgement, and one waiting for EOI.

There are a number of common priority schemas in PICs including hard priorities, specific priorities, and rotating priorities.

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==Well-known types==

One of the best known PICs, the [[Intel 8259|8259A]], was included in the [[x86 architecture|x86]] PC. In modern times, this is not included as a separate chip in an x86 PC, but rather as part of the motherboard's [[Southbridge (computing)|southbridge]] chipset.<ref>{{Cite web| title=82371AB PCI-TO-ISA / IDE Xcelerator (PIIX4) | url=https://www.intel.com/Assets/PDF/datasheet/290562.pdf | archive-url=https://web.archive.org/web/20090203012354/http://www.intel.com:80/Assets/PDF/datasheet/290562.pdf | archive-date=2009-02-03}}</ref> In other cases, it has been replaced by the newer [[Advanced Programmable Interrupt Controller]]s which support more interrupt outputs and more flexible priority schemas.

==See also==

* [[Intel 8259]] -– Notablenotable PIC from Intel

* [[Advanced Programmable Interrupt Controller]] (APIC)

* [[OpenPIC and IBM MPIC]]

* [[Inter-processor interrupt]] (IPI)

* [[Interrupt]]

* [[Interrupt handler]]

* [[Interrupt request]] (IRQ)

* [[Interrupt latency]]

* [[Non-maskable interrupt]] (NMI)

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==Further reading==

More information on the Intel APIC can be found in the ''IA-32 Intel Architecture Software Developer's Manual, Volume 3A: System Programming Guide, Part 1, Chapter 10'', freely available on the [[Intel]] website.

* {{Cite web |date=2023-06-22 |title=Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 3A |url=https://www.intel.com/content/www/us/en/content-details/782158/intel-64-and-ia-32-architectures-software-developer-s-manual-combined-volumes-1-2a-2b-2c-2d-3a-3b-3c-3d-and-4.html?wapkw=intel%2064%20and%20ia-32%20architectures%20software%20developer%27s%20manual&docid=782161 |access-date=2025-03-28 |website=[[Intel]]}}

==References==

{{Reflist}}

==External links==

* [http://www.intel.com/Assets/PDF/manual/253668.pdf IA-32 Intel Architecture Software Developer's Manual, Volume 3A]

* [https://web.archive.org/web/20180408090800/http://www.fullchipdesign.com/tyh/interrupt_controller_vic.htm Interrupt controller and associated registers.]