Quality RTOS & Embedded Software

 Real time embedded FreeRTOS RSS feed 
Real time embedded FreeRTOS mailing list 
Quick Start Supported MCUs PDF Books Trace Tools Ecosystem TCP & FAT Training


ARM spurious IRQ/FIQ

Posted by *anonymous on November 7, 2006

(I thought I posted this earlier, but it didn't appear so I am trying again)

Richard, et al

I have recently been addressing spurious interrupt issues on an LPC2000 processor. There are a variety of issues - related to the pipeline, the VIC, and some peripherals.

The issue I bring to this forum is one in the ARM core itself, due to the pipeline architecture. It involves a scenario in which an IRQ can happen with IRQ/FIQ interrupts disabled. This is discussed fairly well in the Philips User Manuals - I used UM10114_1.pdf.

My concern is with the point that if such an interrupt is processed without taking any special action, then FIQs remain disabled during the whole IRQ processing. There are several possible fixes, but for various reasons I like the one in which interrupts are disabled by first disabling IRQs, then disabling FIQs.

I have made this change in my version of FreeRTOS, but I suggest it should be in the distributed code. This would involve changing everywhere:

MRS    R0, CPSR ORR    R0, R0, #0xC0 MSR    CPSR, R0


MRS    R0, CPSR ORR    R0, R0, #0x80 MSR    CPSR, R0 ORR    R0, R0, #0x40 MSR    CPSR, R0


ARM spurious IRQ/FIQ

Posted by nobody on November 8, 2006

Thank you for your informative post.  I think your suggestion should be adopted.  Some ports use intrinsics to disable the interrupt __disable_interrupt() in IAR for example.  I think these should be changed to assembly also for consistency.

Some demo apps install a spurious interrupt handler and some dont.  Is there a reason for this?

[ Back to the top ]    [ About FreeRTOS ]    [ Sitemap ]    [ ]

Copyright (C) 2004-2010 Richard Barry. Copyright (C) 2010-2016 Real Time Engineers Ltd.
Any and all data, files, source code, html content and documentation included in the FreeRTOSTM distribution or available on this site are the exclusive property of Real Time Engineers Ltd.. See the files license.txt (included in the distribution) and this copyright notice for more information. FreeRTOSTM and FreeRTOS.orgTM are trade marks of Real Time Engineers Ltd.

Latest News:

FreeRTOS V9.0.0 is now available for download.

Free TCP/IP and file system demos for the RTOS

Sponsored Links

⇓ Now With No Code Size Limit! ⇓
⇑ Free Download Without Registering ⇑

FreeRTOS Partners

ARM Connected RTOS partner for all ARM microcontroller cores

Renesas Electronics Gold Alliance RTOS Partner.jpg

Microchip Premier RTOS Partner

RTOS partner of NXP for all NXP ARM microcontrollers

Atmel RTOS partner supporting ARM Cortex-M3 and AVR32 microcontrollers

STMicro RTOS partner supporting ARM7, ARM Cortex-M3, ARM Cortex-M4 and ARM Cortex-M0

Xilinx Microblaze and Zynq partner

Silicon Labs low power RTOS partner

Altera RTOS partner for Nios II and Cortex-A9 SoC

Freescale Alliance RTOS Member supporting ARM and ColdFire microcontrollers

Infineon ARM Cortex-M microcontrollers

Texas Instruments MCU Developer Network RTOS partner for ARM and MSP430 microcontrollers

Cypress RTOS partner supporting ARM Cortex-M3

Fujitsu RTOS partner supporting ARM Cortex-M3 and FM3

Microsemi (previously Actel) RTOS partner supporting ARM Cortex-M3

Atollic Partner

IAR Partner

Keil ARM Partner

Embedded Artists