case OS_DEL_ALWAYS:                                /* Always delete the mailbox                */
             while (pevent->OSEventGrp != 0) {             /* Ready ALL tasks waiting for mailbox      */
                 (void)OS_EventTaskRdy(pevent, (void *)0, OS_STAT_MBOX, OS_STAT_PEND_OK);
             }
#if OS_EVENT_NAME_SIZE > 1
             pevent->OSEventName[0] = '?';                 /* Unknown name                             */
             pevent->OSEventName[1] = OS_ASCII_NUL;
#endif
             pevent->OSEventType    = OS_EVENT_TYPE_UNUSED;
             pevent->OSEventPtr     = OSEventFreeList;     /* Return Event Control Block to free list  */
             pevent->OSEventCnt     = 0;
             OSEventFreeList        = pevent;              /* Get next free event control block        */
             OS_EXIT_CRITICAL();
             if (tasks_waiting == OS_TRUE) {               /* Reschedule only if task(s) were waiting  */
                 OS_Sched();                               /* Find highest priority task ready to run  */
             }
             *perr         = OS_ERR_NONE;
             pevent_return = (OS_EVENT *)0;                /* Mailbox has been deleted                 */
             break;

        default:
             OS_EXIT_CRITICAL();
             *perr         = OS_ERR_INVALID_OPT;
             pevent_return = pevent;
             break;
    }
    return (pevent_return);
}
#endif

/*$PAGE*/
/*
*********************************************************************************************************
*                                      PEND ON MAILBOX FOR A MESSAGE
*
* Description: This function waits for a message to be sent to a mailbox
*
* Arguments  : pevent        is a pointer to the event control block associated with the desired mailbox
*
*              timeout       is an optional timeout period (in clock ticks).  If non-zero, your task will
*                            wait for a message to arrive at the mailbox up to the amount of time
*                            specified by this argument.  If you specify 0, however, your task will wait
*                            forever at the specified mailbox or, until a message arrives.
*
*              perr          is a pointer to where an error message will be deposited.  Possible error
*                            messages are:
*
*                            OS_ERR_NONE         The call was successful and your task received a
*                                                message.
*                            OS_ERR_TIMEOUT      A message was not received within the specified 'timeout'.
*                            OS_ERR_PEND_ABORT   The wait on the mailbox was aborted.
*                            OS_ERR_EVENT_TYPE   Invalid event type
*                            OS_ERR_PEND_ISR     If you called this function from an ISR and the result
*                                                would lead to a suspension.
*                            OS_ERR_PEVENT_NULL  If 'pevent' is a NULL pointer
*                            OS_ERR_PEND_LOCKED  If you called this function when the scheduler is locked
*
* Returns    : != (void *)0  is a pointer to the message received
*              == (void *)0  if no message was received or,
*                            if 'pevent' is a NULL pointer or,
*                            if you didn't pass the proper pointer to the event control block.
*********************************************************************************************************
*/

void  *OSMboxPend (OS_EVENT *pevent, INT16U timeout, INT8U *perr)
{
    void      *pmsg;
    INT8U      pend_stat;
#if OS_CRITICAL_METHOD == 3                           /* Allocate storage for CPU status register      */
    OS_CPU_SR  cpu_sr = 0;
#endif



#if OS_ARG_CHK_EN > 0
    if (perr == (INT8U *)0) {                         /* Validate 'perr'                               */
        return ((void *)0);
    }
    if (pevent == (OS_EVENT *)0) {                    /* Validate 'pevent'                             */
        *perr = OS_ERR_PEVENT_NULL;
        return ((void *)0);
    }
#endif
    if (pevent->OSEventType != OS_EVENT_TYPE_MBOX) {  /* Validate event block type                     */
        *perr = OS_ERR_EVENT_TYPE;
        return ((void *)0);
    }
    if (OSIntNesting > 0) {                           /* See if called from ISR ...                    */
        *perr = OS_ERR_PEND_ISR;                      /* ... can't PEND from an ISR                    */
        return ((void *)0);
    }
    if (OSLockNesting > 0) {                          /* See if called with scheduler locked ...       */
        *perr = OS_ERR_PEND_LOCKED;                   /* ... can't PEND when locked                    */
        return ((void *)0);
    }
    OS_ENTER_CRITICAL();
    pmsg = pevent->OSEventPtr;
    if (pmsg != (void *)0) {                          /* See if there is already a message             */
        pevent->OSEventPtr = (void *)0;               /* Clear the mailbox                             */
        OS_EXIT_CRITICAL();
        *perr = OS_ERR_NONE;
        return (pmsg);                                /* Return the message received (or NULL)         */
    }
    OSTCBCur->OSTCBStat     |= OS_STAT_MBOX;          /* Message not available, task will pend         */
    OSTCBCur->OSTCBStatPend  = OS_STAT_PEND_OK;
    OSTCBCur->OSTCBDly       = timeout;               /* Load timeout in TCB                           */
    OS_EventTaskWait(pevent);                         /* Suspend task until event or timeout occurs    */
    OS_EXIT_CRITICAL();
    OS_Sched();                                       /* Find next highest priority task ready to run  */
    OS_ENTER_CRITICAL();
    if (OSTCBCur->OSTCBStatPend != OS_STAT_PEND_OK) { /* See if we weren't given the message           */
        pend_stat = OSTCBCur->OSTCBStatPend;
        OS_EventTOAbort(pevent);                      /* Timed out, Make task ready                    */
        OS_EXIT_CRITICAL();
        switch (pend_stat) {
            case OS_STAT_PEND_TO:
            default:
                 *perr = OS_ERR_TIMEOUT;              /* Indicate that a timeout occured               */
                 break;

            case OS_STAT_PEND_ABORT:
                 *perr = OS_ERR_PEND_ABORT;           /* Indicate that we aborted                      */
                 break;
        }
        return ((void *)0);                           /* Return a NULL message                         */
    }
    pmsg                    = OSTCBCur->OSTCBMsg;
    OSTCBCur->OSTCBMsg      = (void *)0;              /* Yes, clear message received                   */
    OSTCBCur->OSTCBStat     = OS_STAT_RDY;
    OSTCBCur->OSTCBEventPtr = (OS_EVENT *)0;          /* No longer waiting for event                   */
    OS_EXIT_CRITICAL();
    *perr                   = OS_ERR_NONE;
    return (pmsg);                                    /* Return the message received                   */
}
/*$PAGE*/
/*
*********************************************************************************************************
*                                      ABORT WAITING ON A MESSAGE MAILBOX
*
* Description: This function aborts & readies any tasks currently waiting on a mailbox.  This function 
*              should be used to fault-abort the wait on the mailbox, rather than to normally signal
*              the mailbox via OSMboxPost() or OSMboxPostOpt().
*
* Arguments  : pevent        is a pointer to the event control block associated with the desired mailbox.
*
*              opt           determines the type of ABORT performed:
*                            OS_PEND_OPT_NONE         ABORT wait for a single task (HPT) waiting on the
*                                                     mailbox
*                            OS_PEND_OPT_BROADCAST    ABORT wait for ALL tasks that are  waiting on the
*                                                     mailbox
*
*              perr          is a pointer to where an error message will be deposited.  Possible error
*                            messages are:
*
*                            OS_ERR_NONE         No tasks were     waiting on the mailbox.
*                            OS_ERR_PEND_ABORT   At least one task waiting on the mailbox was readied
*                                                and informed of the aborted wait; check return value 
*                                                for the number of tasks whose wait on the mailbox 
*                                                was aborted.
*                            OS_ERR_EVENT_TYPE   If you didn't pass a pointer to a mailbox.
*                            OS_ERR_PEVENT_NULL  If 'pevent' is a NULL pointer.
*
* Returns    : == 0          if no tasks were waiting on the mailbox, or upon error.
*              >  0          if one or more tasks waiting on the mailbox are now readied and informed.
*********************************************************************************************************
*/

#if OS_MBOX_PEND_ABORT_EN > 0
INT8U  OSMboxPendAbort (OS_EVENT *pevent, INT8U opt, INT8U *perr)
{
    INT8U      nbr_tasks;
#if OS_CRITICAL_METHOD == 3                                /* Allocate storage for CPU status register */
    OS_CPU_SR  cpu_sr = 0;
#endif



#if OS_ARG_CHK_EN > 0
    if (perr == (INT8U *)0) {                              /* Validate 'perr'                          */
        return (0);
    }
    if (pevent == (OS_EVENT *)0) {                         /* Validate 'pevent'                        */
        *perr = OS_ERR_PEVENT_NULL;
        return (0);
    }
#endif
    if (pevent->OSEventType != OS_EVENT_TYPE_MBOX) {       /* Validate event block type                */
        *perr = OS_ERR_EVENT_TYPE;
        return (0);
    }
    OS_ENTER_CRITICAL();
    if (pevent->OSEventGrp != 0) {                         /* See if any task waiting on mailbox?      */
        nbr_tasks = 0;
        switch (opt) {
            case OS_PEND_OPT_BROADCAST:                    /* Do we need to abort ALL waiting tasks?   */
                 while (pevent->OSEventGrp != 0) {         /* Yes, ready ALL tasks waiting on mailbox  */
                     (void)OS_EventTaskRdy(pevent, (void *)0, OS_STAT_MBOX, OS_STAT_PEND_ABORT);
                     nbr_tasks++;
                 }
                 break;
             
            case OS_PEND_OPT_NONE:                         /* No,  ready HPT       waiting on mailbox  */
            default:    
                 (void)OS_EventTaskRdy(pevent, (void *)0, OS_STAT_MBOX, OS_STAT_PEND_ABORT);
                 nbr_tasks++;
                 break;
        }
        OS_EXIT_CRITICAL();
        OS_Sched();                                        /* Find HPT ready to run                    */