• State Accepted Answer
  • Locked Locked
  • Replies 21 replies
  • Answers 1 answer
  • Subscribers 350 subscribers
  • Views 45478 views
  • Users 0 members are here
Options
Related
How was your experience today?
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Cortex-M0: How to switch from one program to another

wshen

Hi,

In my Cortex-M0 project, there are two program images residing at different memory locations: 0x0000_0000 and 0x0010_0000.  Each program has its own vector table.  M0 will boot from the program at 0x0010_0000 then switch to the other program (0x0000_0000) at the end.

What is the correct way to switch to the porgram at 0x0000_0000?  I'm not sure whether the following instructions are correct or not.

     LDR     R6, =0x1                             ; set R6 to 0x0000_0001 due to Thumb mode

     LDR     R0, [R6]

     MOV     SP, R0

     LDR     R1, [R6, #4]

     BX      R1

Can someone please point me the right implementation?  Thanks a lot.

Parents
  • 0

    You would need to change the linker ROM start for each application,
    so they all get their own vector table (below tested for M0+)
    Can take a couple of short cuts as M0 probably will have less than 64K of flash,
    and you compile to 1K boundary.

    

    


    if ( firm1 > firm2)   __asm("movs r0, #0x40");            // upper byte for firmware at 0x4000
    else  __asm("movs r0, #0xA0");                            // upper byte for firmware at 0xA000    
    __asm("lsls r0, r0, #8");  
    __asm("ldr  r1, [r0]");  
    __asm("msr  msp, r1");              // Set new MSP 
    __asm("msr  psp, r1");              // PSP based on SP 
    __asm("ldr  r1, [r0,#0x4]");  
    __asm("mov  pc, r1");               // Jump by changing PC 
    



    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
				
				
				
				
				
		
		
    
			
		
    
	
    

    

    

    • 

	




Reply

    


  • 
	
    


	
			
		
	



    
	
    
		
    
							
					
    
		
    
			
													0
							
			
				
									
							
						
				
			
					
    
	
    

		
		
    
					
    You would need to change the linker ROM start for each application, 
    so they all get their own vector table (below tested for M0+)
    Can take a couple of short cuts as M0 probably will have less than 64K of flash,
    and you compile to 1K boundary.
    

    

    


    if ( firm1 > firm2)   __asm("movs r0, #0x40");            // upper byte for firmware at 0x4000
    else  __asm("movs r0, #0xA0");                            // upper byte for firmware at 0xA000    
    __asm("lsls r0, r0, #8");  
    __asm("ldr  r1, [r0]");  
    __asm("msr  msp, r1");              // Set new MSP 
    __asm("msr  psp, r1");              // PSP based on SP 
    __asm("ldr  r1, [r0,#0x4]");  
    __asm("mov  pc, r1");               // Jump by changing PC 
    



    
			
    

		
		
		
		
	
    
	
    
		
    
			
		
    
	
    
	
    
		
						
				
				
				
				
				
		
		
    
			
		
    
	
    

    

    

    • 





Children
	
No data