Posted on November 09, 2017 at 14:16I want to protect a memory region from writing. I've configured MPU, but it is not generating any faults.Please help.
Here are the registers configuration:
MPU_RNR = 0x00000000; // using region 0
MPU_RBAR = 0x20000000; // base address is 0x20000000
MPU_RASR = 0x0700110B; // Size is 64 bytes, no sub-regions, permission = 7(ro,ro), s=b=c=tex=0
MPU_CTRL = 0x00000001; // enable MPU
Now when I write in this region of memory, it does not generate any exception and writes successfully.
__asm(
'LDR R0, =0x20000000\n\t' // load address in r0, 0x20000000
'MOV R1, 0x77777777\n\t'
'STR R1, [R0,&sharp0]' // write to address 0x200000000
);
This is the definition of handler:
void MemManage_Handler(void)
{
__asm(
'MOV R4, 0x77777777\n\t'
'MOV R5, 0x77777777\n\t'
);
}
I am writing to r4 and r5 just to make sure if the handler was executed or not. This has nothing to do with the rest of the program.
Here's a complete source code:
&sharpdefine MPU_CTRL (*((volatile unsigned long*) 0xE000ED94))
&sharpdefine MPU_RNR (*((volatile unsigned long*) 0xE000ED98))
&sharpdefine MPU_RBAR (*((volatile unsigned long*) 0xE000ED9C))
&sharpdefine MPU_RASR (*((volatile unsigned long*) 0xE000EDA0))
void Registers_Init(void)
{
MPU_RNR = 0x00000000;
MPU_RBAR = 0x20000000;
MPU_RASR = 0x0700110B;
MPU_CTRL = 0x00000001;
}
void MemManage_Handler(void)
{
__asm(
'MOV R4, 0x77777777\n\t'
'MOV R5, 0x77777777\n\t'
);
}
int main(void)
{
Registers_Init();
__asm(
'LDR R0, =0x20000000\n\t'
'MOV R1, 0x77777777\n\t'
'STRD R1, [R0,&sharp0]'
);
return (1);
}
void SystemInit(void)
{
}
#programming #mpu #keil-uvision #fault-exception #stm32f103rb #memmanage-hard-fault
