# Why is software interrupt used in FreeRTOS

**URL:** <https://forums.freertos.org/t/why-is-software-interrupt-used-in-freertos/1898>\
**Category:** Kernel\
**Created:** [July 4, 2010, 5:47am UTC](https://forums.freertos.org/t/why-is-software-interrupt-used-in-freertos/1898 "2010-07-04T05:47:01Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![system](https://d2v6vdsk2p900z.cloudfront.net/original/1X/7fc8fdb729c645aab5b20282bbe34e57cb407be6.jpeg) [@system](https://forums.freertos.org/u/system)\
**Post date:** [July 4, 2010, 5:47am UTC](https://forums.freertos.org/t/why-is-software-interrupt-used-in-freertos/1898/1 "2010-07-04T05:47:01Z")

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**[aeyes](https://sourceforge.net/u/aeyes/)** wrote on [Sunday, July 04, 2010](https://sourceforge.net/p/freertos/discussion/382005/thread/5c0ccf2b/#cdeb):

I am working with FreeRTOS for ARM7\_LPC2106\_GCC. I saw in the startup file a call to vPortYieldProcessor in the SWI interrupt handler. Where is SWI used in FreeRTOS?

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**Author:** ![system](https://d2v6vdsk2p900z.cloudfront.net/original/1X/7fc8fdb729c645aab5b20282bbe34e57cb407be6.jpeg) [@system](https://forums.freertos.org/u/system)\
**Post date:** [July 4, 2010, 7:13am UTC](https://forums.freertos.org/t/why-is-software-interrupt-used-in-freertos/1898/2 "2010-07-04T07:13:44Z")

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**[davedoors](https://sourceforge.net/u/davedoors/)** wrote on [Sunday, July 04, 2010](https://sourceforge.net/p/freertos/discussion/382005/thread/5c0ccf2b/#975b):

Did you try searching the source directory for SWI?

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**Author:** ![rtel](https://d3iykfbgfh8zhg.cloudfront.net/user_avatar/forums.freertos.org/rtel/32/31_2.png) [@rtel](https://forums.freertos.org/u/rtel)\
**Post date:** [July 4, 2010, 7:18am UTC](https://forums.freertos.org/t/why-is-software-interrupt-used-in-freertos/1898/3 "2010-07-04T07:18:37Z")

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**[rtel](https://sourceforge.net/u/rtel/)** wrote on [Sunday, July 04, 2010](https://sourceforge.net/p/freertos/discussion/382005/thread/5c0ccf2b/#b244):

SWI is called each time taskYIELD() is called, which can be from inside an API function or just called directly by a task.

Regards.