fault when jumping from bootloader to application

Hi, Hiowatha

Maybe, I think that the exception is occurred because thumb bit is not set.

Try changing the address of application to  0x00040001.

Thank you.

Thank you both for your suggestions, I appreciate it.

This is how it currently  "seems" to be working: (need to test it more)

HWREG(NVIC_DIS0) = 0xffffffff;
HWREG(NVIC_DIS1) = 0xffffffff;
HWREG(NVIC_DIS2) = 0xffffffff;
HWREG(NVIC_DIS3) = 0xffffffff;
HWREG(NVIC_DIS4) = 0xffffffff;
	
HWREG(NVIC_VTABLE) = APP_START_ADDRESS;

__asm("    ldr     r1, [r0]\n"
      "    mov     sp, r1\n");

__asm("    ldr     r0, [r0, #4]\n"
      "    bx      r0\n");

I will admit that I am not 100% sure why though.

HWREG(NVIC_DIS0) = 0xffffffff;
HWREG(NVIC_DIS1) = 0xffffffff;
HWREG(NVIC_DIS2) = 0xffffffff;
HWREG(NVIC_DIS3) = 0xffffffff;
HWREG(NVIC_DIS4) = 0xffffffff;

The example code I saw this in was jumping from an application in flash to the ROM bootloader.  The comments say that it is disabling all interrupts by doing this before the jump.

Amit, 

      What did you mean by disabling the NVIC handler?

Thanks again!

Hello hiowatha,

Well you did that already as shown in the code post below...

HWREG(NVIC_DIS0) = 0xffffffff;
HWREG(NVIC_DIS1) = 0xffffffff;
HWREG(NVIC_DIS2) = 0xffffffff;
HWREG(NVIC_DIS3) = 0xffffffff;
HWREG(NVIC_DIS4) = 0xffffffff;

Regards

Amit

Hello Amit,

According to the manual of cortex-m, there is restriction that is bit0 of branch address must be 1.

(Refer to http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0552a/BABEFHAE.html)

So, I think that the address of application must be 0x00040001 in the sample code posted by hiowatha.

Is it  wrong?

Regards

Kyoman

Hello Kyoman,

You are right that LSB has to be 1. But when compiled through standard compilers like the one in CCS, IAR, Keil, the compiler and linkers take care of the same. In this case Hiowatha is using a compiled image and loading the PC with the content of the Address in the 0x4 location which will have the correct PC value +1

Regards

Amit

Hi, Amit,

what do you mean by "Using a RTOS will make things a little bit more complex"?

I am using TivaC1294NCPDT, and I also need to bootloader to APP with RTOS. I think I have done everything, but it just doesn't work. The attached are: 1.The map of app. 2.Bin of app. 3.cmd of app and boot. 4.boot loader code.

When I step into the bootloader, it looks to me the Jump2App is not correct. Here is what I see about the values of R0 and R1:

1. After "HWREG(NVIC_VTABLE) = __Flash_Start_App_Run;", R0 is 0x20023C88 and R1 is 0xE000ED08

2. After the first two asm, R0 is still 0x20023C88 and R1 is changed to 0xBEBEBEBE (I think this is not a valid value)

3. After the next asm ("ldr     r0, [r0, #4]"), R0 is changed to 0xBEBEBEBE.

4. And then, PC becomes "0xBEBEBEBE", which of course it not a correct address.

I think the final R0 should be "0002caa1", which is "ENTRY POINT SYMBOL: "_c_int00"  address: 0002caa1" in map file.

The application code could run normally with debugger.

Could you help me check this issue? Thanks

 BootAndAP.zip

Hello Jianyi,

The application's address must have the SP and PC mapped to the first two location of the application address space. The r0 shall contain the address of the application so that the ldr then load the sp with content of r0 and then load r0 with r0+0x4 and branch to r0.

Regards
Amit

Thanks, Amit. I wonder why the asm code from hiowatha doesn't work for me. I am not good at asm code, so could you please take a look for me?

I found the issue. It should be " HWREG(NVIC_VTABLE) = &__Flash_Start_App_Run", rather than " HWREG(NVIC_VTABLE) = __Flash_Start_App_Run".
Thanks

hiowatha,

I'm coming across this same problem that you were having. My bootloader and application is RTOS and I tried using the same code you have above but it's still failing. It'll jump to the application but then a fault is generated. Did you have to do anything on the VTABLE for the application to get it to work? Because if I use a simple application without interrupts or RTOS, then the jump works. So I'm guessing once the application generated an interrupt, the application faulted.

Thanks.

If my memory serves me right... I believe this was answered in another post related to this problem:
e2e.ti.com/.../347628

Again going off of memory, for me the fix was to disable interrupts prior to jumping the application's address:

here's how the current code looks like now:


#define FLASH_DEFAULT 0xFFFFFFFF

// disable all interrupts
HWREG(NVIC_DIS0) = FLASH_DEFAULT;
HWREG(NVIC_DIS1) = FLASH_DEFAULT;
HWREG(NVIC_DIS2) = FLASH_DEFAULT;
HWREG(NVIC_DIS3) = FLASH_DEFAULT;
HWREG(NVIC_DIS4) = FLASH_DEFAULT;

// reset vector table to application starting address
HWREG(NVIC_VTABLE) = i_address;

// jump (note: does not return from this point)
__asm(" ldr r1, [r0]\n"
" mov sp, r1\n");

__asm(" ldr r0, [r0, #4]\n"
" bx r0\n");

hope that helps!

hiowatha,

Thanks for the response. I did see the previous thread and I'm using basically the same code to perform the jump but I'm getting a fault when the application starts executing. I'm thinking that it has something to do with the VTABLE. Do you recall if there was anything special you had to do with the VTABLE in defining the interrupts, like offsetting the address of the handler or changing the vtable memory from the default RAM_BASE?

Thanks.