OS_TCB  *ptcb1;
    OS_TCB  *ptcb2;


    OSTCBList     = (OS_TCB *)0;                                 /* TCB Initialization                       */
    for (i = 0; i < (OS_LOWEST_PRIO + 1); i++) {                 /* Clear the priority table                 */
        OSTCBPrioTbl[i] = (OS_TCB *)0;
    }
    ptcb1 = &OSTCBTbl[0];
    ptcb2 = &OSTCBTbl[1];
    for (i = 0; i < (OS_MAX_TASKS + OS_N_SYS_TASKS - 1); i++) {  /* Init. list of free TCBs                  */
        ptcb1->OSTCBNext = ptcb2;
        ptcb1++;
        ptcb2++;
    }
    ptcb1->OSTCBNext = (OS_TCB *)0;                              /* Last OS_TCB                              */
    OSTCBFreeList    = &OSTCBTbl[0];
}
/*$PAGE*/
/*
*********************************************************************************************************
*                                              SCHEDULER
*
* Description: This function is called by other uC/OS-II services to determine whether a new, high
*              priority task has been made ready to run.  This function is invoked by TASK level code
*              and is not used to reschedule tasks from ISRs (see OSIntExit() for ISR rescheduling).
*
* Arguments  : none
*
* Returns    : none
*
* Notes      : 1) This function is INTERNAL to uC/OS-II and your application should not call it.
*              2) Rescheduling is prevented when the scheduler is locked (see OS_SchedLock())
*********************************************************************************************************
*/

void  OS_Sched (void)
{
#if OS_CRITICAL_METHOD == 3                            /* Allocate storage for CPU status register     */
    OS_CPU_SR  cpu_sr;
#endif    
    INT8U      y;


    OS_ENTER_CRITICAL();
    if ((OSIntNesting == 0) && (OSLockNesting == 0)) { /* Sched. only if all ISRs done & not locked    */
        y             = OSUnMapTbl[OSRdyGrp];          /* Get pointer to HPT ready to run              */
        OSPrioHighRdy = (INT8U)((y << 3) + OSUnMapTbl[OSRdyTbl[y]]);
        if (OSPrioHighRdy != OSPrioCur) {              /* No Ctx Sw if current task is highest rdy     */
            OSTCBHighRdy = OSTCBPrioTbl[OSPrioHighRdy];
            OSCtxSwCtr++;                              /* Increment context switch counter             */
            OS_TASK_SW();                              /* Perform a context switch                     */
        }
    }
    OS_EXIT_CRITICAL();
}
/*$PAGE*/
/*
*********************************************************************************************************
*                                              IDLE TASK
*
* Description: This task is internal to uC/OS-II and executes whenever no other higher priority tasks
*              executes because they are ALL waiting for event(s) to occur.
*
* Arguments  : none
*
* Returns    : none
*
* Note(s)    : 1) OSTaskIdleHook() is called after the critical section to ensure that interrupts will be
*                 enabled for at least a few instructions.  On some processors (ex. Philips XA), enabling
*                 and then disabling interrupts didn't allow the processor enough time to have interrupts
*                 enabled before they were disabled again.  uC/OS-II would thus never recognize
*                 interrupts.
*              2) This hook has been added to allow you to do such things as STOP the CPU to conserve 
*                 power.
*********************************************************************************************************
*/

void  OS_TaskIdle (void *pdata)
{
#if OS_CRITICAL_METHOD == 3                      /* Allocate storage for CPU status register           */
    OS_CPU_SR  cpu_sr;
#endif    
    
    
    pdata = pdata;                               /* Prevent compiler warning for not using 'pdata'     */
    for (;;) {
        OS_ENTER_CRITICAL();
        OSIdleCtr++;
        OS_EXIT_CRITICAL();
        OSTaskIdleHook();                        /* Call user definable HOOK                           */
    }
}
/*$PAGE*/
/*
*********************************************************************************************************
*                                            STATISTICS TASK
*
* Description: This task is internal to uC/OS-II and is used to compute some statistics about the
*              multitasking environment.  Specifically, OS_TaskStat() computes the CPU usage.
*              CPU usage is determined by:
*
*                                          OSIdleCtr
*                 OSCPUUsage = 100 * (1 - ------------)     (units are in %)
*                                         OSIdleCtrMax
*
* Arguments  : pdata     this pointer is not used at this time.
*
* Returns    : none
*
* Notes      : 1) This task runs at a priority level higher than the idle task.  In fact, it runs at the
*                 next higher priority, OS_IDLE_PRIO-1.
*              2) You can disable this task by setting the configuration #define OS_TASK_STAT_EN to 0.
*              3) We delay for 5 seconds in the beginning to allow the system to reach steady state and
*                 have all other tasks created before we do statistics.  You MUST have at least a delay
*                 of 2 seconds to allow for the system to establish the maximum value for the idle
*                 counter.
*********************************************************************************************************
*/

#if OS_TASK_STAT_EN > 0
void  OS_TaskStat (void *pdata)
{
#if OS_CRITICAL_METHOD == 3                      /* Allocate storage for CPU status register           */
    OS_CPU_SR  cpu_sr;
#endif    
    INT32U     run;
    INT32U     max;
    INT8S      usage;


    pdata = pdata;                               /* Prevent compiler warning for not using 'pdata'     */
    while (OSStatRdy == FALSE) {
        OSTimeDly(2 * OS_TICKS_PER_SEC);         /* Wait until statistic task is ready                 */
    }
    max = OSIdleCtrMax / 100L;
    for (;;) {
        OS_ENTER_CRITICAL();
        OSIdleCtrRun = OSIdleCtr;                /* Obtain the of the idle counter for the past second */
        run          = OSIdleCtr;
        OSIdleCtr    = 0L;                       /* Reset the idle counter for the next second         */
        OS_EXIT_CRITICAL();
        if (max > 0L) {
            usage = (INT8S)(100L - run / max);
            if (usage >= 0) {                    /* Make sure we don't have a negative percentage      */
                OSCPUUsage = usage;
            } else {
                OSCPUUsage = 0;
            }
        } else {
            OSCPUUsage = 0;
            max        = OSIdleCtrMax / 100L;
        }
        OSTaskStatHook();                        /* Invoke user definable hook                         */
        OSTimeDly(OS_TICKS_PER_SEC);             /* Accumulate OSIdleCtr for the next second           */
    }
}
#endif
/*$PAGE*/
/*
*********************************************************************************************************
*                                            INITIALIZE TCB
*
* Description: This function is internal to uC/OS-II and is used to initialize a Task Control Block when
*              a task is created (see OSTaskCreate() and OSTaskCreateExt()).
*
* Arguments  : prio          is the priority of the task being created
*
*              ptos          is a pointer to the task's top-of-stack assuming that the CPU registers
*                            have been placed on the stack.  Note that the top-of-stack corresponds to a
*                            'high' memory location is OS_STK_GROWTH is set to 1 and a 'low' memory
*                            location if OS_STK_GROWTH is set to 0.  Note that stack growth is CPU
*                            specific.
*
*              pbos          is a pointer to the bottom of stack.  A NULL pointer is passed if called by
*                            'OSTaskCreate()'.
*
*              id            is the task's ID (0..65535)
*
*              stk_size      is the size of the stack (in 'stack units').  If the stack units are INT8Us
*                            then, 'stk_size' contains the number of bytes for the stack.  If the stack
*                            units are INT32Us then, the stack contains '4 * stk_size' bytes.  The stack
*                            units are established by the #define constant OS_STK which is CPU
*                            specific.  'stk_size' is 0 if called by 'OSTaskCreate()'.
*
*              pext          is a pointer to a user supplied memory area that is used to extend the task
*                            control block.  This allows you to store the contents of floating-point
*                            registers, MMU registers or anything else you could find useful during a
*                            context switch.  You can even assign a name to each task and store this name
*                            in this TCB extension.  A NULL pointer is passed if called by OSTaskCreate().
*
*              opt           options as passed to 'OSTaskCreateExt()' or,
*                            0 if called from 'OSTaskCreate()'.
*
* Returns    : OS_NO_ERR         if the call was successful
*              OS_NO_MORE_TCB    if there are no more free TCBs to be allocated and thus, the task cannot
*                                be created.
*
* Note       : This function is INTERNAL to uC/OS-II and your application should not call it.
*********************************************************************************************************
*/

INT8U  OS_TCBInit (INT8U prio, OS_STK *ptos, OS_STK *pbos, INT16U id, INT32U stk_size, void *pext, INT16U opt)
{
#if OS_CRITICAL_METHOD == 3                                /* Allocate storage for CPU status register */
    OS_CPU_SR  cpu_sr;
#endif    
    OS_TCB    *ptcb;


    OS_ENTER_CRITICAL();
    ptcb = OSTCBFreeList;                                  /* Get a free TCB from the free TCB list    */
    if (ptcb != (OS_TCB *)0) {
        OSTCBFreeList        = ptcb->OSTCBNext;            /* Update pointer to free TCB list          */
        OS_EXIT_CRITICAL();
        ptcb->OSTCBStkPtr    = ptos;                       /* Load Stack pointer in TCB                */
        ptcb->OSTCBPrio      = (INT8U)prio;                /* Load task priority into TCB              */
        ptcb->OSTCBStat      = OS_STAT_RDY;                /* Task is ready to run                     */
        ptcb->OSTCBDly       = 0;                          /* Task is not delayed                      */

#if OS_TASK_CREATE_EXT_EN > 0
        ptcb->OSTCBExtPtr    = pext;                       /* Store pointer to TCB extension           */
        ptcb->OSTCBStkSize   = stk_size;                   /* Store stack size                         */
        ptcb->OSTCBStkBottom = pbos;                       /* Store pointer to bottom of stack         */
        ptcb->OSTCBOpt       = opt;                        /* Store task options                       */
        ptcb->OSTCBId        = id;                         /* Store task ID                            */
#else
        pext                 = pext;                       /* Prevent compiler warning if not used     */
        stk_size             = stk_size;
        pbos                 = pbos;
        opt                  = opt;
        id                   = id;
#endif

#if OS_TASK_DEL_EN > 0
        ptcb->OSTCBDelReq    = OS_NO_ERR;
#endif

        ptcb->OSTCBY         = prio >> 3;                  /* Pre-compute X, Y, BitX and BitY          */
        ptcb->OSTCBBitY      = OSMapTbl[ptcb->OSTCBY];
        ptcb->OSTCBX         = prio & 0x07;
        ptcb->OSTCBBitX      = OSMapTbl[ptcb->OSTCBX];

#if OS_EVENT_EN > 0
        ptcb->OSTCBEventPtr  = (OS_EVENT *)0;              /* Task is not pending on an event          */
#endif

#if (OS_VERSION >= 251) && (OS_FLAG_EN > 0) && (OS_MAX_FLAGS > 0) && (OS_TASK_DEL_EN > 0)
        ptcb->OSTCBFlagNode  = (OS_FLAG_NODE *)0;          /* Task is not pending on an event flag     */
#endif

#if (OS_MBOX_EN > 0) || ((OS_Q_EN > 0) && (OS_MAX_QS > 0))
        ptcb->OSTCBMsg       = (void *)0;                  /* No message received                      */
#endif

#if OS_VERSION >= 204
        OSTCBInitHook(ptcb);
#endif

        OSTaskCreateHook(ptcb);                            /* Call user defined hook                   */
        
        OS_ENTER_CRITICAL();
        OSTCBPrioTbl[prio] = ptcb;
        ptcb->OSTCBNext    = OSTCBList;                    /* Link into TCB chain                      */
        ptcb->OSTCBPrev    = (OS_TCB *)0;
        if (OSTCBList != (OS_TCB *)0) {
            OSTCBList->OSTCBPrev = ptcb;
        }
        OSTCBList               = ptcb;
        OSRdyGrp               |= ptcb->OSTCBBitY;         /* Make task ready to run                   */
        OSRdyTbl[ptcb->OSTCBY] |= ptcb->OSTCBBitX;
        OS_EXIT_CRITICAL();
        return (OS_NO_ERR);
    }
    OS_EXIT_CRITICAL();
    return (OS_NO_MORE_TCB);
}