BaseType_t xPortStartScheduler( void )
{
uint32_t ulAPSR;
/* Only continue if the CPU is not in User mode. The CPU must be in a
Privileged mode for the scheduler to start. */
__asm( "MRS ulAPSR, APSR" );
ulAPSR &= portAPSR_MODE_BITS_MASK;
configASSERT( ulAPSR != portAPSR_USER_MODE );
if( ulAPSR != portAPSR_USER_MODE )
{
/* Only continue if the binary point value is set to its lowest possible
setting. See the comments in vPortValidateInterruptPriority() below for
more information. */
configASSERT( ( portICCBPR_BINARY_POINT_REGISTER & portBINARY_POINT_BITS ) <= portMAX_BINARY_POINT_VALUE );
if( ( portICCBPR_BINARY_POINT_REGISTER & portBINARY_POINT_BITS ) <= portMAX_BINARY_POINT_VALUE )
{
/* Start the timer that generates the tick ISR. */
configSETUP_TICK_INTERRUPT();
__enable_irq();
vPortRestoreTaskContext();
}
}
/* Will only get here if xTaskStartScheduler() was called with the CPU in
a non-privileged mode or the binary point register was not set to its lowest
possible value. */
return 0;
}
BaseType_t xPortStartScheduler( void )
{
/* Setup the hardware to generate the tick. Interrupts are disabled when
this function is called. */
configSETUP_TICK_INTERRUPT();
/* Restore the context of the first task that is going to run. */
vPortStartFirstTask();
/* Execution should not reach here as the tasks are now running!
prvSetupTimerInterrupt() is called here to prevent the compiler outputting
a warning about a statically declared function not being referenced in the
case that the application writer has provided their own tick interrupt
configuration routine (and defined configSETUP_TICK_INTERRUPT() such that
their own routine will be called in place of prvSetupTimerInterrupt()). */
prvSetupTimerInterrupt();
return pdTRUE;
}
BaseType_t xPortStartScheduler( void )
{
/* Use pxCurrentTCB just so it does not get optimised away. */
if( pxCurrentTCB != NULL )
{
/* Call an application function to set up the timer that will generate
the tick interrupt. This way the application can decide which
peripheral to use. If tickless mode is used then the default
implementation defined in this file (which uses CMT0) should not be
overridden. */
configSETUP_TICK_INTERRUPT();
/* Enable the software interrupt. */
_IEN( _ICU_SWINT ) = 1;
/* Ensure the software interrupt is clear. */
_IR( _ICU_SWINT ) = 0;
/* Ensure the software interrupt is set to the kernel priority. */
_IPR( _ICU_SWINT ) = configKERNEL_INTERRUPT_PRIORITY;
/* Start the first task. */
prvStartFirstTask();
}
/* Execution should not reach here as the tasks are now running!
prvSetupTimerInterrupt() is called here to prevent the compiler outputting
a warning about a statically declared function not being referenced in the
case that the application writer has provided their own tick interrupt
configuration routine (and defined configSETUP_TICK_INTERRUPT() such that
their own routine will be called in place of prvSetupTimerInterrupt()). */
prvSetupTimerInterrupt();
/* Just to make sure the function is not optimised away. */
( void ) vSoftwareInterruptISR();
/* Should not get here. */
return pdFAIL;
}
