supervisor mode

the other thing I don't understand is that the uasrt is not working - could there be a problem with the stack size within the supervisor stack size? I get no error during the program but I get no output by usart, too.

Moreover is it not common to run the whole programm in user mode and only if a excerption occured it runs in FIQ, IRQ mode or SWI mode, where I could changed mode...?

Is it a good choice to change the mode in the startup code file? but where? there are init-area for each mode - and the last mode is the user mode (is it not right, that the last mode is the mode where the processor starts the c-file code? And in the user mode is no I-bit or F-bit set?

tobi

the other thing I don't understand is that the uasrt is not working - could there be a problem with the stack size within the supervisor stack size? I get no error during the program but I get no output by usart, too.

Moreover is it not common to run the whole programm in user mode and only if a excerption occured it runs in FIQ, IRQ mode or SWI mode, where I could changed mode...?

Is it a good choice to change the mode in the startup code file? but where? there are init-area for each mode - and the last mode is the user mode (is it not right, that the last mode is the mode where the processor starts the c-file code? And in the user mode is no I-bit or F-bit set?

tobi

maybe anyone of you have a explanation for me - why I'm not able to get into user mode...

I have nothing changed in the startup code file...

;  Enter Supervisor Mode and set its Stack Pointer
                MSR     CPSR_c, #Mode_SVC:OR:I_Bit:OR:F_Bit
                MOV     SP, R0
                SUB     R0, R0, #SVC_Stack_Size

;  Enter User Mode and set its Stack Pointer
                MSR     CPSR_c, #Mode_USR
                IF      :DEF:__MICROLIB

                EXPORT __initial_sp

                ELSE

                MOV     SP, R0
                SUB     SL, SP, #USR_Stack_Size

                ENDIF


; Enter the C code

                IMPORT  __main
                LDR     R0, =__main
                BX      R0


                IF      :DEF:__MICROLIB

                EXPORT  __heap_base
                EXPORT  __heap_limit

                ELSE

My C-code is as small as possible - one file one function...

int main(void)
 {
 while(1);
 }

the only thing I changed was that I installed the scatter-file (options for target -> linker)...

From this moment on, I'm not able to get into the user mode, when I start the application. When I use no scatter-file, the processor will start up in user mode...
Is there a option in the keil enviroment, which I must select to run in user mode...

best regards
tobi

I'm right if I say that I'm only able to install my own scatter file in supervisor mode? And therefore the processor will start up (the main function) in supervisor mode? How can I changed to the user mode within the main function? Or is it better to change to the user mode within the startup file?

MSR     CPSR_c, #Mode_USR

tobi

ok I know my mistake - it was in the scatter file... I forgot to install the *.o (RESET, +First) directive.

But could somebody explain me why the processor enters in the supervisor mode, if this directive are not installed?

tobi

It has already been explained to you. The processor always starts in it's toughest mode.

It needs to process instructions that tells it to enter user mode. With a broken scatter file, the application startup code is not run, so no instruction switches the processor into the user mode.

It has already been explained to you. The processor always starts in it's toughest mode.

Yes I know that there must be an explanation which defines the user mode. And now I understand why it is not working in the user mode, because I never enterd the startup code file (because I have not installed a suitable section for it...) -> thanks for your answer - now it is clear for me.

Which sections are recommend to install in such a scatter-file? I have one section for the external flash (with the startup-code included), one section for the internal RAM and one section for the external RAM (only for the use of big structures and buffers from the peripherie).

But is it for example recommend to install my own heap and stack size within the scatter-file - or the vector table (for data abort handler, undefined handler and so on)?

How is it possible to install one section only for incomming data from all peripherials e.g. usart or usb. Do I have to install only a EMPTY section?

ARM_SECTION 0x20000000 EMPTY 0x8000

and now I'm able to say

int *ptr_buffer = 0x20000000;

tobi

Now I want to use two load regions - one for each storage (flash and internal ram) - but now I get the error
No Algorithm found for: 00200000H - 0020000FH

LOAD_FLASH 0x10000000 0xFFFFFF                     ; start address and length
{

        EXTERN_FLASH 0x10000000
        {
                *.o (RESET, +First)
                *(+RO)
        }
}

LOAD_SRAM 0x00200000 0xFFFFF
{
        INTERN_RAM 0x00200000
        {
                *(+RW,+ZI)
        }
}

The internal RAM is from 0x00200000 to 0x002FFFFF.

tobi

Now I get another stupid error - I have one section for one c-file (only +RW, +ZI) and the +RO data of this section where placed by the compiler to the default address 0x0000000. I thought that it would be enough to create one region with *(+RO) where all RO data would be stored????

LOAD_FLASH 0x10000000 0xFFFFFF                     ; start address and length
{

        EXTERN_FLASH 0x10000000 0xFFFFFF
        {
                RM9200.o (RESET, +First)
                *(+RO)

        }

        SRAM 0x20000000 0xFFFFFF
        {
                timer.o (+RW,+ZI)
        }

        BUFFER_SRAM 0x21000000 EMPTY 0x2000000
        {

        }

        INTERN_RAM 0x200000 0xFFFFF
        {
                *(+RW,+ZI)
        }
}

tobi

If I wrote

timer.o (+RO)

in the executing section EXTERN-FLASH

I get the warning, that the compiler will removed unused sections (timer.o (RO)).

But I want to have all RO data from the c-file timer.c within the external flash.

tobi