AM2434: Can't access banked register using msr or mrs

Shine

Part Number: AM2434

Hello Champs,

As can be seen from the architecture manual of armv7 r, as shown in the figure, for banked registers, it can be accessed via MRS and MSR. Now customer writes to access sp_usr, lr_usr, sp, lr, The statements of cpsr, spsr, spsr_svc, as shown in the figure, show that sp_usr cannot be operated with either MRS or mov. lr_usr and Spsr_svc, so how to access the banked register? How to compile? What does the compiler set?

Thanks
Regards
Shine

over 2 years ago

0 QJ Wang over 2 years ago

TI__Guru**** 200846 points

Hi Shine,

sp_<mode> and spsr_<mode> are not supported. You can access the registers of other modes after setting the mode using ARM CPS instruction. For example:

CPS #ARM_MODE_SVC

MRS R0, SPSR

0 guxl24 over 2 years ago in reply to QJ Wang

Prodigy 150 points

I want to obtain R13_ Usr and R14_ USR in undefined or abort mode, so I switched to USR mode using CPS to obtain it, but switching back to undefined or abort mode in user mode is not allowed. So how should I go back to undefined or abort mode？As the picture shows.

0 QJ Wang over 2 years ago in reply to guxl24

TI__Guru**** 200846 points

You can not switch to privileged mode directly from user mode. You need to do a SVC call. Please refer to the app note below:

Interrupt and Exception Handling on Hercules ARM Cortex-R4/5-Based Microcontrollers

Arm-based microcontrollers

Arm-based microcontrollers forum

AM2434: Can't access banked register using msr or mrs