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isr relocate

 
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Martin H
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isr relocate
PostPosted: Wed Oct 19, 2005 8:06 am     Reply with quote
I have relocated the interrupt vectors to make my bootloader work. The routine below is located on adderss 0x08 but if I don't make a call to it in my program the compiler removes the function (some kind of opimization maybe). I have looked through the manual but can't find a directive to make the code "stick" withut some extra call

Code:

#org 0x08, 0x24
void isr_relocate(void)
{
#asm
   // Address 0x0008 is the hardware High priority interrupt
   TSTFSZ BootloaderActive            // if bootloader active
   goto LOADER_ISR_ADDR               // then jump to bootloader ISR
   goto APP_BEGIN + 0x08            // jump to application ISR

   nop
   nop
   nop

   // Address 0x0018 is the hardware Low priority interrupt
   TSTFSZ BootloaderActive            // if bootloader active
   goto LOADER_ISR_ADDR + 0x10      // then jump to bootloader ISR
   goto APP_BEGIN + 0x18            // jump to application ISR
#endasm
}

// Some other place in the code (this is what I want to avoid)
...
  if(some_variable_that_never_will_be_true)
    isr_relocate();
...



Thanks
Martin[/code]
asmallri



Joined: 12 Aug 2004
Posts: 1635
Location: Perth, Australia

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PostPosted: Wed Oct 19, 2005 10:24 am     Reply with quote
Here is some early code I used when I was migrating from assembler to CCS C and need to retian my assembler interrupt hanlders because I used multiple high priority interrupts on the PIC18F which were not supported by CCS at the time.

I fooled the compiler into thinking the interrupt vectors were located elsewhere then I put the real vectors in place. The compiler did not optimise out this code.


Code:

// prevent the compiler sticking code between 0x0004 and 0x0007
#build(reset=0x00:0x07)


// fool the compiler to allow access to the real high and low priority vectors
#build(interrupt=0x028)
#org 0x0020, 0x002f {}

   /* Map the high priority interrupt vector */
#org 0x0008, 0x000f
void my_hp_intr (void)
   {
   #asm
   goto   0x0100
   #endasm
   }

   /* Map the low priority interrupt vector */
#org 0x0018, 0x001f
void my_lp_intr (void)
   {
   #asm
   goto   0x0200
   #endasm
   }



#org 0x0100, 0x01ff
void HPIntrHdlr(void) {
   #asm ASIS

....

_________________
Regards, Andrew

http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!!
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