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Cortex R5 ARM processor

Pankaj Verma

HI All,

I am trying to use FREE RTOS in cortex R5 dual core MCU.

Initially the MCU is in Supervisor mode. But in main function, i want to be a processor mode will be in system mode(0x1F).

But i do not find any instruction how to switch from supervisor mode(0x13) to system mode(0x1F).

Why we need to switch from supervisor mode to system mode if both are working in privilege mode because for the unitization of the RTOS, scheduler should be in system mode. 

Can any one please tell me how to switch from supervisor mode to system mode.

I have tried to switch but the system will be reset automatically after change in system mode.

 have see the mode in CPSR register.

Thanks and regard 

Pankaj verma

Parents
  • 0 in reply to Ronan Synnott

    HI Synnott,

    I tell you whole application scenario.

    I am using TMS570LC43 MCU with RTOS. Here we are also using safeTI diagnostic library for MCU self test condition.

    So initially when the system power ON the system work on Supervisor mode "0x13". 

    After initialization of all the CPU core registers, clock, RAM, Flash, other memory, peripherals etc.

    The code going inside main loop. After that we need to initialize RTOS Scheduler.

    For initialization of RTOS Scheduler we need to change mode from supervisor to system mode otherwise the schedular will not successfully initialize. The scheduler is fail.

    And for safeTI diagnostic we need to run all the safety test cases in supervisor mode only.

    That is the reason we need to change from supervisor to system mode and after that we need to change it again in supervisor mode when the safety test will run again.

      

    Thanks 

    Pankaj Verma

Reply
  • 0 in reply to Ronan Synnott

    HI Synnott,

    I tell you whole application scenario.

    I am using TMS570LC43 MCU with RTOS. Here we are also using safeTI diagnostic library for MCU self test condition.

    So initially when the system power ON the system work on Supervisor mode "0x13". 

    After initialization of all the CPU core registers, clock, RAM, Flash, other memory, peripherals etc.

    The code going inside main loop. After that we need to initialize RTOS Scheduler.

    For initialization of RTOS Scheduler we need to change mode from supervisor to system mode otherwise the schedular will not successfully initialize. The scheduler is fail.

    And for safeTI diagnostic we need to run all the safety test cases in supervisor mode only.

    That is the reason we need to change from supervisor to system mode and after that we need to change it again in supervisor mode when the safety test will run again.

      

    Thanks 

    Pankaj Verma

Children
  • 0 Arm Employee Badge in reply to Pankaj Verma

    It is standard for an RTOS to run in SVC mode, and its applications to run in USR mode.

    Applications running in SYS mode use the same physical registers as USR, but with privileged permissions.

    I don't know why the scheduler init code would need to run in SYS specifically.

    Assuming what you wish to do is valid... I've written (but not tested) code to switch to SYS. Would this work for you?

    	push {r0, r1, lr}	// preserve r0, r1, lr on SVC stack
	
	mov r1, sp			// copy sp_svc into r1
	
    mrs r0, cpsr		// read cpsr into r0
    orr r0, r0, 0x1f	// set mode bits to SYS
    msr cpsr, r0		// switch to SYS mode
	
	mov sp, r1			// copy sp_svc (r1) into sp_sys
	
	pop {r0, r1, pc}	// return in SYS mode using SVC stack

  • 0 in reply to Ronan Synnott

    HI Synnott,

    Yes you are right and i have tried below code as per your suggestion.

    It is jump to the supervisor mode to system mode by using below instruction.

    .def _CPU_system_mode_Switch
    .asmFunc
    _CPU_system_mode_Switch


    MOV R1, LR
    MOV R2, SP
    MRS r0, CPSR                     //read cpsr into r0
    orr r0, r0, #0x1f                       //set mode to SYS
    MSR cpsr, r0                           //write r0 back to cpsr
    MOV LR, R1
    MOV SP, R2
    bx lr                                         //return
    .endasmfunc

    Is it correct?

    I will also try your code.

    Can you tell me that, if a application jump to system mode to supervisor mode at any time and vise versa  . It will not effect to running application and RTOS behavior's.

    Thanks for your great help, Have a nice day.

    Pankaj Verma

  • 0 Arm Employee Badge in reply to Pankaj Verma

    The code looks correct to me, but as I said, I don't believe this is really what you want to do...

    Your application should run in SYS mode (ideally USR mode), and the RTOS in SVC mode, with independent stacks. The RTOS will manage switching between applications.

    Regards. Ronan