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Unprotect SYSCON3 in XC164CS device

John Brown

Hi everybody;
Im trying to manage the peripherals in a XC164CS device while the main program is executing. I belive that the SYSCON3 register is protected because when I try to writting in it, the initial value remains and don't change. Am I right?
How do you unprotect this register? Thank you very much.

  • 0

    I think you are correct. This is a Dave tool generated function to unlock protected registers. You can call it prior to modifying SYSCON3.

    //****************************************************************************
// @Function      void MAIN_vUnlockProtecReg(void)
//
//----------------------------------------------------------------------------
// @Description   This function makes it possible to write one protected
//                register. After calling of this function and write on the
//                protected register is the security level set to low
//                protected mode.
//
//----------------------------------------------------------------------------
// @Returnvalue   None
//
//----------------------------------------------------------------------------
// @Parameters    None
//
//----------------------------------------------------------------------------
// @Date          11/6/2009
//
//****************************************************************************

// USER CODE BEGIN (UnlockProtecReg,1)

// USER CODE END

void MAIN_vUnlockProtecReg(void)
{
  uword uwPASSWORD;

  if((SCUSLS & 0x1800) == 0x0800)      // if low protected mode
  {

    uwPASSWORD = SCUSLS & 0x00FF;
    uwPASSWORD = (~uwPASSWORD) & 0x00FF;
    SCUSLC = 0x8E00 | uwPASSWORD;      // command 4

  }  // end if low protected mode

  if((SCUSLS & 0x1800) == 0x1800)      // if write protected mode
  {
    SCUSLC = 0xAAAA;                   // command 0
    SCUSLC = 0x5554;                   // command 1

    uwPASSWORD = SCUSLS & 0x00FF;
    uwPASSWORD = (~uwPASSWORD) & 0x00FF;

    SCUSLC = 0x9600 | uwPASSWORD;      // command 2
    SCUSLC = 0x0800;                   // command 3; new PASSWOR is 0x00

    uwPASSWORD = SCUSLS & 0x00FF;
    uwPASSWORD = (~uwPASSWORD) & 0x00FF;
    SCUSLC = 0x8E00 | uwPASSWORD;      // command 4

  }  // end if write protected mode

} //  End of function MAIN_vUnlockProtecReg

  • 0 in reply to Walt Conley

    Thank you very much Walt:
    It works well! :)