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


M7 r0p1 port

Posted by cman12345 on January 26, 2016


I was trying to find out more information about what M7 errata the pendSV handler is working around. I couldn't locate the errata doc and was hoping someone could point me to it. For reference I was looking at the "Errata workaround" lines below. Thanks!

~~~~ void xPortPendSVHandler( void ) { /* This is a naked function. */

__asm volatile
"	mrs r0, psp							\n"
"	isb									\n"
"										\n"
"	ldr	r3, pxCurrentTCBConst			\n" /* Get the location of the current TCB. */
"	ldr	r2, [r3]						\n"
"										\n"
"	tst r14, #0x10						\n" /* Is the task using the FPU context?  If so, push high vfp registers. */
"	it eq								\n"
"	vstmdbeq r0!, {s16-s31}				\n"
"										\n"
"	stmdb r0!, {r4-r11, r14}			\n" /* Save the core registers. */
"										\n"
"	str r0, [r2]						\n" /* Save the new top of stack into the first member of the TCB. */
"										\n"
"	stmdb sp!, {r3}						\n"
"	mov r0, %0 							\n"
"	cpsid i								\n" /* Errata workaround. */
"	msr basepri, r0						\n"
"	dsb									\n"
"   isb									\n"
"	cpsie i								\n" /* Errata workaround. */


M7 r0p1 port

Posted by rtel on January 26, 2016

This was something found by our testing. As I recall (?) the basepri update does not take effect immediately, and it was necessary to place the "cpsid i" "cpsie i" instructions around the update to basepri to ensure modifying its value has an effect by the end of the isb instruction. You will find those additional asm instructions are the only difference between the M7r0p1 port and the standard M4F port.


M7 r0p1 port

Posted by cman12345 on January 26, 2016

Ok, thanks for the info!

[ 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