Hi Thomas,
Thank you for your response.
The piece of code where in i am trying this is something like this

#include <sys/neutrino.h> // Inlcude already for many other functions like interruptattach,mmap_device_io

       intrspin_t *clrSpnLck ;

	if( ThreadCtl( _NTO_TCTL_IO, 0 ) != -1 )
	{
                //I tried this as per  the manual
		//memset( clrSpnLck, 1, sizeof( *clrSpnLck ) ); //Code crashed either here if enabled

		//clrSpnLck->value = 1; //Tried this just if the variable in the structure intrspin_t was to be initialized

		InterruptLock(SetSpnLck_g); //Or code crashed here

		regData  &= (~(1 << bitPos));  //volatile uint32_t regData and uint8_t bitPos

		InterruptUnlock(SetSpnLck_g);

	}
Is there anything i am missing