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44 * Implementation of functions defined in portable.h for the MSP430 port.
47 /* Constants required for hardware setup.  The tick ISR runs off the ACLK,
48  * not the MCLK. */
53 /* We require the address of the pxCurrentTCB variable, but don't want to know
58 /* Most ports implement critical sections by placing the interrupt flags on
59  * the stack before disabling interrupts.  Exiting the critical section is then
60  * simply a case of popping the flags from the stack.  As mspgcc does not use
61  * a frame pointer this cannot be done as modifying the stack will clobber all
62  * the stack variables.  Instead each task maintains a count of the critical
63  * section nesting depth.  Each time a critical section is entered the count is
64  * incremented.  Each time a critical section is left the count is decremented -
65  * with interrupts only being re-enabled if the count is zero.
67  * usCriticalNesting will get set to zero when the scheduler starts, but must
68  * not be initialised to zero as this will cause problems during the startup
74  * Macro to save a task context to the task stack.  This simply pushes all the
75  * general purpose msp430 registers onto the stack, followed by the
76  * usCriticalNesting value used by the task.  Finally the resultant stack
77  * pointer value is saved into the task control block so it can be retrieved
78  * the next time the task executes.
100  * Macro to restore a task context from the task stack.  This is effectively
101  * the reverse of portSAVE_CONTEXT().  First the stack pointer value is
102  * loaded from the task control block.  Next the value for usCriticalNesting
103  * used by the task is retrieved from the stack - followed by the value of all
104  * the general purpose msp430 registers.
106  * The bic instruction ensures there are no low power bits set in the status
107  * register that is about to be popped from the stack.
132  * Sets up the periodic ISR used for the RTOS tick.  This uses timer 0, but
133  * could have alternatively used the watchdog timer or timer 1.
139  * Initialise the stack of a task to look exactly as if a call to
142  * See the header file portable.h.
149      *  Place a few bytes of known values on the bottom of the stack.  in pxPortInitialiseStack()
160     /* The msp430 automatically pushes the PC then SR onto the stack before  in pxPortInitialiseStack()
161      * executing an ISR.  We want the stack to look just as if this has happened  in pxPortInitialiseStack()
162      * so place a pointer to the start of the task on the stack first - followed  in pxPortInitialiseStack()
163      * by the flags we want the task to use when it starts up. */  in pxPortInitialiseStack()
169     /* Next the general purpose registers. */  in pxPortInitialiseStack()
193     /* When the task starts is will expect to find the function parameter in  in pxPortInitialiseStack()
198     /* The code generated by the mspgcc compiler does not maintain separate  in pxPortInitialiseStack()
199      * stack and frame pointers. The portENTER_CRITICAL macro cannot therefore  in pxPortInitialiseStack()
200      * use the stack as per other ports.  Instead a variable is used to keep  in pxPortInitialiseStack()
201      * track of the critical section nesting.  This variable has to be stored  in pxPortInitialiseStack()
202      * as part of the task context and is initially set to zero. */  in pxPortInitialiseStack()
205     /* Return a pointer to the top of the stack we have generated so this can  in pxPortInitialiseStack()
206      * be stored in the task control block for the task. */  in pxPortInitialiseStack()
213     /* Setup the hardware to generate the tick.  Interrupts are disabled when  in xPortStartScheduler()
217     /* Restore the context of the first task that is going to run. */  in xPortStartScheduler()
220     /* Should not get here as the tasks are now running! */  in xPortStartScheduler()
227     /* It is unlikely that the MSP430 port will get stopped.  If required simply  in vPortEndScheduler()
228      * disable the tick interrupt here. */  in vPortEndScheduler()
235  * The first thing we do is save the registers so we can use a naked attribute.
240     /* We want the stack of the task being saved to look exactly as if the task  in vPortYield()
241      * was saved during a pre-emptive RTOS tick ISR.  Before calling an ISR the  in vPortYield()
242      * msp430 places the status register onto the stack.  As this is a function  in vPortYield()
247     /* Save the context of the current task. */  in vPortYield()
250     /* Switch to the highest priority task that is ready to run. */  in vPortYield()
253     /* Restore the context of the new task. */  in vPortYield()
259  * Hardware initialisation to generate the RTOS tick.  This uses timer 0
260  * but could alternatively use the watchdog timer or timer 1.
264     /* Ensure the timer is stopped. */  in prvSetupTimerInterrupt()
267     /* Run the timer of the ACLK. */  in prvSetupTimerInterrupt()
273     /* Set the compare match value according to the tick rate we want. */  in prvSetupTimerInterrupt()
276     /* Enable the interrupts. */  in prvSetupTimerInterrupt()
288  * The interrupt service routine used depends on whether the pre-emptive
296  * the context is saved at the start of vPortYieldFromTick().  The tick
297  * count is incremented after the context is saved.
302         /* Save the context of the interrupted task. */  in prvTickISR()
305         /* Increment the tick count then switch to the highest priority task  in prvTickISR()
312         /* Restore the context of the new task. */  in prvTickISR()
319  * Tick ISR for the cooperative scheduler.  All this does is increment the