Resetting HCS12 using software

[RChapman]

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Posted: Tue Sep 20, 2005 5:40 pm    

Is it possible, to cause the HCS122 to reset itself using softare.

Posted: Wed Sep 21, 2005 8:09 pm    

yes surely

just activate the cop, register COPCTL
and trigger directly with a false value written to the ARMCOP register.

Normally you would write 0x55 and then 0xAA; try some other value and you will get a reset at once

e.g.
COPCTL = 0x01; // cop activated with shortest timeout
ARMCOP = 0x47; // her we will get kicked by the dog

Posted: Thu Sep 22, 2005 4:55 pm    

 am assuming that Quantum needs to "simulate" a Power-On reset.
If you make sure that the COP reset vector is the same as the Power-On reset vector, Cristian's method should work perfectly.

I tried the suggested approach, it didn't work with me. I read a little in the "CPU12 Reference Manual" and figured the reason is probably that the HC12 differentiates between 4 types of Reset (Power-On, External Reset, COP/Watchdog and Clock Monitor Reset). The first two types use the same Reset vector, the other two have their own vectors.

Another possibility which I have used is to wire the (open drain) /RESET pin to an I/O pin (possibly with a diode in between?). Now if you make the I/O pin be a LOW output, it resets the controller (making the I/O pin an input).

Notice:
a) without the diode the I/O pin should not be set to be a HIGH output (potential short-circuit)
b) this is not a pure SW method

[javadshabani]

thank you It worked well

[wilero17]

I was sawing some tips in the forum about the watchdog timer and I have some questions.

actually
I'm working with the HCS12 microcontroller and I need to use the
watchdog timer in order to do  reset. I've configurated the COPCTL
register with 71 (COPCTL=71) the program
stay in a infinite for loop showing a caracter ascii in the
hyperterminal until the watchdog finish. The problem is:  after the
watchdog timer has finished the program doesn't reset o may be yes, but
I can't see more caracters in the hyperterminal until I do a manual
reset.  I've attached the program. I hope that you can help me. many
thanks.

This is the main function:



 void main(void) {
  /* put your own code here */

  char msn[20]={"Hola"};
  char msn1[5]={"."}; 
  word cont1X;
  word cont2X;

  cont2X=0;
  while(cont2X<=5000)
  {
    cont2X++;
    cont1X=0;
    while(cont1X<=100)
    {
      asm BRN *;
      cont1X++;    
    }    
  }

  SCI0BD = 12;

  SCI0CR1 = 0x00;

  SCI0CR2 = 0x04;

  vfnSCITxMsg(msn);
  COPCTL=71;
  
  for(;;) {
  cont2X=0;
  while(cont2X<=5000)
  {
    cont2X++;
    cont1X=0;
    while(cont1X<=100)
    {
      asm BRN *;
      cont1X++;    
    }    
  }
  vfnSCITxMsg(msn1);
  } /* loop forever */
  /* please make sure that you never leave main */
}