+ uint32_t ulReloadValue, ulCompleteTickPeriods, ulCompletedSysTickDecrements, ulSysTickCTRL;\r
+ TickType_t xModifiableIdleTime;\r
+\r
+ /* Make sure the SysTick reload value does not overflow the counter. */\r
+ if( xExpectedIdleTime > xMaximumPossibleSuppressedTicks )\r
+ {\r
+ xExpectedIdleTime = xMaximumPossibleSuppressedTicks;\r
+ }\r
+\r
+ /* Stop the SysTick momentarily. The time the SysTick is stopped for\r
+ is accounted for as best it can be, but using the tickless mode will\r
+ inevitably result in some tiny drift of the time maintained by the\r
+ kernel with respect to calendar time. */\r
+ portNVIC_SYSTICK_CTRL_REG &= ~portNVIC_SYSTICK_ENABLE_BIT;\r
+\r
+ /* Calculate the reload value required to wait xExpectedIdleTime\r
+ tick periods. -1 is used because this code will execute part way\r
+ through one of the tick periods. */\r
+ ulReloadValue = portNVIC_SYSTICK_CURRENT_VALUE_REG + ( ulTimerCountsForOneTick * ( xExpectedIdleTime - 1UL ) );\r
+ if( ulReloadValue > ulStoppedTimerCompensation )\r
+ {\r
+ ulReloadValue -= ulStoppedTimerCompensation;\r
+ }\r
+\r
+ /* Enter a critical section but don't use the taskENTER_CRITICAL()\r
+ method as that will mask interrupts that should exit sleep mode. */\r
+ __disable_interrupt();\r
+\r
+ /* If a context switch is pending or a task is waiting for the scheduler\r
+ to be unsuspended then abandon the low power entry. */\r
+ if( eTaskConfirmSleepModeStatus() == eAbortSleep )\r
+ {\r
+ /* Restart from whatever is left in the count register to complete\r
+ this tick period. */\r
+ portNVIC_SYSTICK_LOAD_REG = portNVIC_SYSTICK_CURRENT_VALUE_REG;\r
+\r
+ /* Restart SysTick. */\r
+ portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT;\r
+\r
+ /* Reset the reload register to the value required for normal tick\r
+ periods. */\r
+ portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;\r
+\r
+ /* Re-enable interrupts - see comments above __disable_interrupt()\r
+ call above. */\r
+ __enable_interrupt();\r
+ }\r
+ else\r
+ {\r
+ /* Set the new reload value. */\r
+ portNVIC_SYSTICK_LOAD_REG = ulReloadValue;\r
+\r
+ /* Clear the SysTick count flag and set the count value back to\r
+ zero. */\r
+ portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;\r
+\r
+ /* Restart SysTick. */\r
+ portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT;\r
+\r
+ /* Sleep until something happens. configPRE_SLEEP_PROCESSING() can\r
+ set its parameter to 0 to indicate that its implementation contains\r
+ its own wait for interrupt or wait for event instruction, and so wfi\r
+ should not be executed again. However, the original expected idle\r
+ time variable must remain unmodified, so a copy is taken. */\r
+ xModifiableIdleTime = xExpectedIdleTime;\r
+ configPRE_SLEEP_PROCESSING( xModifiableIdleTime );\r
+ if( xModifiableIdleTime > 0 )\r
+ {\r
+ __DSB();\r
+ __WFI();\r
+ __ISB();\r
+ }\r
+ configPOST_SLEEP_PROCESSING( xExpectedIdleTime );\r
+\r
+ /* Stop SysTick. Again, the time the SysTick is stopped for is\r
+ accounted for as best it can be, but using the tickless mode will\r
+ inevitably result in some tiny drift of the time maintained by the\r
+ kernel with respect to calendar time. */\r
+ ulSysTickCTRL = portNVIC_SYSTICK_CTRL_REG;\r
+ portNVIC_SYSTICK_CTRL_REG = ( ulSysTickCTRL & ~portNVIC_SYSTICK_ENABLE_BIT );\r
+\r
+ /* Re-enable interrupts - see comments above __disable_interrupt()\r
+ call above. */\r
+ __enable_interrupt();\r
+\r
+ if( ( ulSysTickCTRL & portNVIC_SYSTICK_COUNT_FLAG_BIT ) != 0 )\r
+ {\r
+ uint32_t ulCalculatedLoadValue;\r
+\r
+ /* The tick interrupt has already executed, and the SysTick\r
+ count reloaded with ulReloadValue. Reset the\r
+ portNVIC_SYSTICK_LOAD_REG with whatever remains of this tick\r
+ period. */\r
+ ulCalculatedLoadValue = ( ulTimerCountsForOneTick - 1UL ) - ( ulReloadValue - portNVIC_SYSTICK_CURRENT_VALUE_REG );\r
+\r
+ /* Don't allow a tiny value, or values that have somehow\r
+ underflowed because the post sleep hook did something\r
+ that took too long. */\r
+ if( ( ulCalculatedLoadValue < ulStoppedTimerCompensation ) || ( ulCalculatedLoadValue > ulTimerCountsForOneTick ) )\r
+ {\r
+ ulCalculatedLoadValue = ( ulTimerCountsForOneTick - 1UL );\r
+ }\r
+\r
+ portNVIC_SYSTICK_LOAD_REG = ulCalculatedLoadValue;\r
+\r
+ /* The tick interrupt handler will already have pended the tick\r
+ processing in the kernel. As the pending tick will be\r
+ processed as soon as this function exits, the tick value\r
+ maintained by the tick is stepped forward by one less than the\r
+ time spent waiting. */\r
+ ulCompleteTickPeriods = xExpectedIdleTime - 1UL;\r
+ }\r
+ else\r
+ {\r
+ /* Something other than the tick interrupt ended the sleep.\r
+ Work out how long the sleep lasted rounded to complete tick\r
+ periods (not the ulReload value which accounted for part\r
+ ticks). */\r
+ ulCompletedSysTickDecrements = ( xExpectedIdleTime * ulTimerCountsForOneTick ) - portNVIC_SYSTICK_CURRENT_VALUE_REG;\r
+\r
+ /* How many complete tick periods passed while the processor\r
+ was waiting? */\r
+ ulCompleteTickPeriods = ulCompletedSysTickDecrements / ulTimerCountsForOneTick;\r
+\r
+ /* The reload value is set to whatever fraction of a single tick\r
+ period remains. */\r
+ portNVIC_SYSTICK_LOAD_REG = ( ( ulCompleteTickPeriods + 1 ) * ulTimerCountsForOneTick ) - ulCompletedSysTickDecrements;\r
+ }\r
+\r
+ /* Restart SysTick so it runs from portNVIC_SYSTICK_LOAD_REG\r
+ again, then set portNVIC_SYSTICK_LOAD_REG back to its standard\r
+ value. The critical section is used to ensure the tick interrupt\r
+ can only execute once in the case that the reload register is near\r
+ zero. */\r
+ portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;\r
+ portENTER_CRITICAL();\r
+ {\r
+ portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT;\r
+ vTaskStepTick( ulCompleteTickPeriods );\r
+ portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;\r
+ }\r
+ portEXIT_CRITICAL();\r
+ }\r