/* Switch to supervisor mode */
    NU_SUPERVISOR_MODE();

    /* Move input timer pointer into internal pointer.  */
    timer =  (TM_APP_TCB *) timer_ptr;


#ifdef  NU_ENABLE_STACK_CHECK

    /* Call stack checking function to check for an overflow condition.  */
    TCT_Check_Stack();

#endif

#ifdef  NU_ENABLE_HISTORY

    /* Make an entry that corresponds to this function in the system history
       log.  */
    HIC_Make_History_Entry(NU_RESET_TIMER_ID, (UNSIGNED) timer,
                       (UNSIGNED) expiration_routine, (UNSIGNED) initial_time);

#endif

    /* Protect against access to the active timer list.  */
    TCT_System_Protect();

    /* Determine if this timer is active.  An active timer cannot be
       reset.  */
    if (timer -> tm_enabled)
    {

        /* Indicate that the timer is active by returning the proper status. */
        status =  NU_NOT_DISABLED;

#ifdef INCLUDE_PROVIEW
        _RTProf_DumpTimer(RT_PROF_RESET_TIMER,timer,RT_PROF_FAIL);
#endif /* INCLUDE_PROVIEW */

    }
    else
    {

        /* Load the timer with the appropriate values.  */
        timer -> tm_expiration_routine =    expiration_routine;
        timer -> tm_expirations =           0;
        timer -> tm_initial_time =          initial_time;
        timer -> tm_reschedule_time =       reschedule_time;

        /* Indicate successful completion status.  */
        status =  NU_SUCCESS;
#ifdef INCLUDE_PROVIEW
        _RTProf_DumpTimer(RT_PROF_RESET_TIMER,timer,RT_PROF_OK);
#endif /* INCLUDE_PROVIEW */

    }

    /* Release protection.  */
    TCT_Unprotect();

    /* Determine if the timer needs to be enabled.  */
    if ((status == NU_SUCCESS) && (enable == NU_ENABLE_TIMER))

        /* Activate the timer.  */
        TMS_Control_Timer(timer_ptr, NU_ENABLE_TIMER);

    /* Return to user mode */
    NU_USER_MODE();

    /* Return completion status.  */
    return(status);
}


/*************************************************************************/
/*                                                                       */
/* FUNCTION                                                              */
/*                                                                       */
/*      TMS_Control_Timer                                                */
/*                                                                       */
/* DESCRIPTION                                                           */
/*                                                                       */
/*      This function either enables or disables the specified timer.    */
/*      If the timer is already in the desired state, simply leave it    */
/*      alone.                                                           */
/*                                                                       */
/* CALLED BY                                                             */
/*                                                                       */
/*      Application                                                      */
/*      TMSE_Control_Timer                Error checking shell           */
/*                                                                       */
/* CALLS                                                                 */
/*                                                                       */
/*      [HIC_Make_History_Entry]            Make entry in history log    */
/*      [TCT_Check_Stack]                   Stack checking function      */
/*      TCT_System_Protect                  Protect the active list      */
/*      TCT_Unprotect                       Release protection           */
/*      TMC_Start_Timer                     Start a timer                */
/*      TMC_Stop_Timer                      Stop a timer                 */
/*                                                                       */
/* INPUTS                                                                */
/*                                                                       */
/*      app_timer                           Timer control block pointer  */
/*      enable                              Disable/enable timer option  */
/*                                                                       */
/* OUTPUTS                                                               */
/*                                                                       */
/*      NU_SUCCESS                          If service is successful     */
/*                                                                       */
/* HISTORY                                                               */
/*                                                                       */
/*         DATE                    REMARKS                               */
/*                                                                       */
/*      03-01-1993      Created initial version 1.0                      */
/*      04-19-1993      Verified version 1.0                             */
/*      03-01-1994      Modified protection logic to use                 */
/*                        system protection, changed                     */
/*                        function prototype, resulting                  */
/*                        in version 1.1                                 */
/*                                                                       */
/*      03-18-1994      Verified version 1.1                             */
/*                                                                       */
/*************************************************************************/
STATUS  TMS_Control_Timer(NU_TIMER *app_timer, OPTION enable)
{

R1 TM_APP_TCB  *timer;                      /* Timer control block ptr   */
TM_TCB         *timer_ptr;                  /* Actual timer pointer      */
UNSIGNED        time;                       /* Variable to hold request  */
NU_SUPERV_USER_VARIABLES

    /* Switch to supervisor mode */
    NU_SUPERVISOR_MODE();

    /* Move input timer pointer into internal pointer.  */
    timer =  (TM_APP_TCB *) app_timer;


#ifdef  NU_ENABLE_STACK_CHECK

    /* Call stack checking function to check for an overflow condition.  */
    TCT_Check_Stack();

#endif

#ifdef  NU_ENABLE_HISTORY

    /* Make an entry that corresponds to this function in the system history
       log.  */
    HIC_Make_History_Entry(NU_CONTROL_TIMER_ID, (UNSIGNED) timer,
                                        (UNSIGNED) enable, (UNSIGNED) 0);

#endif

    /* Protect against simultaneous access to the active timer list.  */
    TCT_System_Protect();

    /* Setup pointer to actual timer part of the control block.  */
    timer_ptr =  &(timer -> tm_actual_timer);

    /* Determine what type of request is present.  */
    if ((enable == NU_ENABLE_TIMER) && (!timer -> tm_enabled))
    {

        /* Enable timer request is present and timer is currently disabled.  */

        /* Determine how to setup the remaining field in the actual timer. */
        if (timer -> tm_expirations)

            /* Use reschedule time since this timer has expired previously. */
            time =  timer -> tm_reschedule_time;
        else

            /* Use initial time since this timer has never expired.  */
            time =  timer -> tm_initial_time;

        /* Mark the application timer as enabled.  */
        timer -> tm_enabled =  NU_TRUE;

        /* Call the start timer routine to actually start the timer.  */
        TMC_Start_Timer(&(timer -> tm_actual_timer), time);
    }
    else if ((enable == NU_DISABLE_TIMER) && (timer -> tm_enabled))
    {

        /* Disable timer request is present and timer is currently enabled.  */
        TMC_Stop_Timer(timer_ptr);

        /* Mark the timer as disabled.  */
        timer -> tm_enabled =  NU_FALSE;
    }

#ifdef INCLUDE_PROVIEW
        _RTProf_DumpTimer(RT_PROF_CONTROL_TIMER,timer,RT_PROF_OK);
#endif /* INCLUDE_PROVIEW */
    /* Release protection.  */
    TCT_Unprotect();

    /* Return to user mode */
    NU_USER_MODE();

    /* Return the completion status.  */
    return(NU_SUCCESS);
}