0301_APP/_uCOS-III/uC-CPU/cpu_c.c

/*
*********************************************************************************************************
*                                                uC/CPU
*                                    CPU CONFIGURATION & PORT LAYER
*
*                          (c) Copyright 2004-2011; Micrium, Inc.; Weston, FL
*
*               All rights reserved.  Protected by international copyright laws.
*
*               uC/CPU is provided in source form to registered licensees ONLY.  It is 
*               illegal to distribute this source code to any third party unless you receive 
*               written permission by an authorized Micrium representative.  Knowledge of 
*               the source code may NOT be used to develop a similar product.
*
*               Please help us continue to provide the Embedded community with the finest 
*               software available.  Your honesty is greatly appreciated.
*
*               You can contact us at www.micrium.com.
*********************************************************************************************************
*/

/*
*********************************************************************************************************
*
*                                            CPU PORT FILE
*
*                                            ARM-Cortex-M3
*                                            IAR C Compiler
*
* Filename      : cpu_c.c
* Version       : V1.28.01.00
* Programmer(s) : JJL
*                 BAN
*********************************************************************************************************
*/


/*
*********************************************************************************************************
*                                            INCLUDE FILES
*********************************************************************************************************
*/

#include  <cpu.h>
#include  <cpu_core.h>

#include  <lib_def.h>


/*$PAGE*/
/*
*********************************************************************************************************
*                                            LOCAL DEFINES
*********************************************************************************************************
*/

#define  CPU_INT_SRC_POS_MAX                  ((((CPU_REG_NVIC_NVIC + 1) & 0x1F) * 32) + 16)

#define  CPU_BIT_BAND_SRAM_REG_LO                 0x20000000
#define  CPU_BIT_BAND_SRAM_REG_HI                 0x200FFFFF
#define  CPU_BIT_BAND_SRAM_BASE                   0x22000000


#define  CPU_BIT_BAND_PERIPH_REG_LO               0x40000000
#define  CPU_BIT_BAND_PERIPH_REG_HI               0x400FFFFF
#define  CPU_BIT_BAND_PERIPH_BASE                 0x42000000


/*
*********************************************************************************************************
*                                           LOCAL CONSTANTS
*********************************************************************************************************
*/


/*
*********************************************************************************************************
*                                          LOCAL DATA TYPES
*********************************************************************************************************
*/


/*
*********************************************************************************************************
*                                            LOCAL TABLES
*********************************************************************************************************
*/


/*
*********************************************************************************************************
*                                       LOCAL GLOBAL VARIABLES
*********************************************************************************************************
*/


/*
*********************************************************************************************************
*                                      LOCAL FUNCTION PROTOTYPES
*********************************************************************************************************
*/


/*
*********************************************************************************************************
*                                     LOCAL CONFIGURATION ERRORS
*********************************************************************************************************
*/


/*$PAGE*/
/*
*********************************************************************************************************
*                                          CPU_BitBandClr()
*
* Description : Clear bit in bit-band region.
*
* Argument(s) : addr            Byte address in memory space.
*
*               bit_nbr         Bit number in byte.
*
* Return(s)   : none.
*
* Caller(s)   : Application.
*
* Note(s)     : none.
*********************************************************************************************************
*/

void  CPU_BitBandClr (CPU_ADDR    addr,
                      CPU_INT08U  bit_nbr)
{
    CPU_ADDR  bit_word_off;
    CPU_ADDR  bit_word_addr;


    if ((addr >= CPU_BIT_BAND_SRAM_REG_LO) &&
        (addr <= CPU_BIT_BAND_SRAM_REG_HI)) {
        bit_word_off  = ((addr - CPU_BIT_BAND_SRAM_REG_LO  ) * 32) + (bit_nbr * 4);
        bit_word_addr = CPU_BIT_BAND_SRAM_BASE   + bit_word_off;

      *(volatile CPU_INT32U *)(bit_word_addr) = 0;

    } else if ((addr >= CPU_BIT_BAND_PERIPH_REG_LO) &&
               (addr <= CPU_BIT_BAND_PERIPH_REG_HI)) {
        bit_word_off  = ((addr - CPU_BIT_BAND_PERIPH_REG_LO) * 32) + (bit_nbr * 4);
        bit_word_addr = CPU_BIT_BAND_PERIPH_BASE + bit_word_off;

      *(volatile CPU_INT32U *)(bit_word_addr) = 0;
    }
}


/*$PAGE*/
/*
*********************************************************************************************************
*                                          CPU_BitBandSet()
*
* Description : Set bit in bit-band region.
*
* Argument(s) : addr            Byte address in memory space.
*
*               bit_nbr         Bit number in byte.
*
* Return(s)   : none.
*
* Caller(s)   : Application.
*
* Note(s)     : none.
*********************************************************************************************************
*/

void  CPU_BitBandSet (CPU_ADDR    addr,
                      CPU_INT08U  bit_nbr)
{
    CPU_ADDR  bit_word_off;
    CPU_ADDR  bit_word_addr;


    if ((addr >= CPU_BIT_BAND_SRAM_REG_LO) &&
        (addr <= CPU_BIT_BAND_SRAM_REG_HI)) {
        bit_word_off  = ((addr - CPU_BIT_BAND_SRAM_REG_LO  ) * 32) + (bit_nbr * 4);
        bit_word_addr = CPU_BIT_BAND_SRAM_BASE   + bit_word_off;

      *(volatile CPU_INT32U *)(bit_word_addr) = 1;

    } else if ((addr >= CPU_BIT_BAND_PERIPH_REG_LO) &&
               (addr <= CPU_BIT_BAND_PERIPH_REG_HI)) {
        bit_word_off  = ((addr - CPU_BIT_BAND_PERIPH_REG_LO) * 32) + (bit_nbr * 4);
        bit_word_addr = CPU_BIT_BAND_PERIPH_BASE + bit_word_off;

      *(volatile CPU_INT32U *)(bit_word_addr) = 1;
    }
}


/*$PAGE*/
/*
*********************************************************************************************************
*                                           CPU_IntSrcDis()
*
* Description : Disable an interrupt source.
*
* Argument(s) : pos     Position of interrupt vector in interrupt table :
*
*                           0       Invalid (see Note #1a).
*                           1       Invalid (see Note #1b).
*                           2       Non-maskable interrupt.
*                           3       Hard Fault.
*                           4       Memory Management.
*                           5       Bus Fault.
*                           6       Usage Fault.
*                           7-10    Reserved.
*                           11      SVCall
*                           12      Debug monitor.
*                           13      Reserved
*                           14      PendSV.
*                           15      SysTick.
*                           16+     External Interrupt.
*
* Return(s)   : none.
*
* Caller(s)   : Application.
*
* Note(s)     : (1) Several table positions do not contain interrupt sources :
*
*                   (a) Position 0 contains the stack pointer.
*                   (b) Positions 7-10, 13 are reserved.
*
*               (2) Several interrupts cannot be disabled/enabled :
*
*                   (a) Reset.
*                   (b) NMI.
*                   (c) Hard fault.
*                   (d) SVCall.
*                   (e) Debug monitor.
*                   (f) PendSV.
*
*               (3) The maximum Cortex-M3 table position is 256.  A particular Cortex-M3 may have fewer
*                   than 240 external exceptions and, consequently, fewer than 256 table positions.
*                   This function assumes that the specified table position is valid if the interrupt
*                   controller type register's INTLINESNUM field is large enough so that the position
*                   COULD be valid.
*********************************************************************************************************
*/
/*$PAGE*/
void  CPU_IntSrcDis (CPU_INT08U  pos)
{
    CPU_INT08U  group;
    CPU_INT08U  pos_max;
    CPU_INT08U  nbr;
    CPU_SR_ALLOC();


    switch (pos) {
        case CPU_INT_STK_PTR:                                   /* ---------------- INVALID OR RESERVED --------------- */
        case CPU_INT_RSVD_07:
        case CPU_INT_RSVD_08:
        case CPU_INT_RSVD_09:
        case CPU_INT_RSVD_10:
        case CPU_INT_RSVD_13:
             break;


                                                                /* ----------------- SYSTEM EXCEPTIONS ---------------- */
        case CPU_INT_RESET:                                     /* Reset (see Note #2).                                 */
        case CPU_INT_NMI:                                       /* Non-maskable interrupt (see Note #2).                */
        case CPU_INT_HFAULT:                                    /* Hard fault (see Note #2).                            */
        case CPU_INT_SVCALL:                                    /* SVCall (see Note #2).                                */
        case CPU_INT_DBGMON:                                    /* Debug monitor (see Note #2).                         */
        case CPU_INT_PENDSV:                                    /* PendSV (see Note #2).                                */
             break;

        case CPU_INT_MEM:                                       /* Memory management.                                   */
             CPU_CRITICAL_ENTER();
             CPU_REG_NVIC_SHCSR &= ~CPU_REG_NVIC_SHCSR_MEMFAULTENA;
             CPU_CRITICAL_EXIT();
             break;

        case CPU_INT_BUSFAULT:                                  /* Bus fault.                                           */
             CPU_CRITICAL_ENTER();
             CPU_REG_NVIC_SHCSR &= ~CPU_REG_NVIC_SHCSR_BUSFAULTENA;
             CPU_CRITICAL_EXIT();
             break;

        case CPU_INT_USAGEFAULT:                                /* Usage fault.                                         */
             CPU_CRITICAL_ENTER();
             CPU_REG_NVIC_SHCSR &= ~CPU_REG_NVIC_SHCSR_USGFAULTENA;
             CPU_CRITICAL_EXIT();
             break;

        case CPU_INT_SYSTICK:                                   /* SysTick.                                             */
             CPU_CRITICAL_ENTER();
             CPU_REG_NVIC_ST_CTRL &= ~CPU_REG_NVIC_ST_CTRL_ENABLE;
             CPU_CRITICAL_EXIT();
             break;


                                                                /* ---------------- EXTERNAL INTERRUPT ---------------- */
        default:
            pos_max = CPU_INT_SRC_POS_MAX;
            if (pos < pos_max) {                                /* See Note #3.                                         */
                 group = (pos - 16) / 32;
                 nbr   = (pos - 16) % 32;

                 CPU_CRITICAL_ENTER();
                 CPU_REG_NVIC_CLREN(group) = DEF_BIT(nbr);
                 CPU_CRITICAL_EXIT();
             }
             break;
    }
}


/*$PAGE*/
/*
*********************************************************************************************************
*                                           CPU_IntSrcEn()
*
* Description : Enable an interrupt source.
*
* Argument(s) : pos     Position of interrupt vector in interrupt table (see 'CPU_IntSrcDis()').
*
* Return(s)   : none.
*
* Caller(s)   : Application.
*
* Note(s)     : (1) See 'CPU_IntSrcDis()  Note #1'.
*
*               (2) See 'CPU_IntSrcDis()  Note #2'.
*
*               (3) See 'CPU_IntSrcDis()  Note #3'.
*********************************************************************************************************
*/

void  CPU_IntSrcEn (CPU_INT08U  pos)
{
    CPU_INT08U  group;
    CPU_INT08U  nbr;
    CPU_INT08U  pos_max;
    CPU_SR_ALLOC();


    switch (pos) {
        case CPU_INT_STK_PTR:                                   /* ---------------- INVALID OR RESERVED --------------- */
        case CPU_INT_RSVD_07:
        case CPU_INT_RSVD_08:
        case CPU_INT_RSVD_09:
        case CPU_INT_RSVD_10:
        case CPU_INT_RSVD_13:
             break;


                                                                /* ----------------- SYSTEM EXCEPTIONS ---------------- */
        case CPU_INT_RESET:                                     /* Reset (see Note #2).                                 */
        case CPU_INT_NMI:                                       /* Non-maskable interrupt (see Note #2).                */
        case CPU_INT_HFAULT:                                    /* Hard fault (see Note #2).                            */
        case CPU_INT_SVCALL:                                    /* SVCall (see Note #2).                                */
        case CPU_INT_DBGMON:                                    /* Debug monitor (see Note #2).                         */
        case CPU_INT_PENDSV:                                    /* PendSV (see Note #2).                                */
             break;

        case CPU_INT_MEM:                                       /* Memory management.                                   */
             CPU_CRITICAL_ENTER();
             CPU_REG_NVIC_SHCSR |= CPU_REG_NVIC_SHCSR_MEMFAULTENA;
             CPU_CRITICAL_EXIT();
             break;

        case CPU_INT_BUSFAULT:                                  /* Bus fault.                                           */
             CPU_CRITICAL_ENTER();
             CPU_REG_NVIC_SHCSR |= CPU_REG_NVIC_SHCSR_BUSFAULTENA;
             CPU_CRITICAL_EXIT();
             break;

        case CPU_INT_USAGEFAULT:                                /* Usage fault.                                         */
             CPU_CRITICAL_ENTER();
             CPU_REG_NVIC_SHCSR |= CPU_REG_NVIC_SHCSR_USGFAULTENA;
             CPU_CRITICAL_EXIT();
             break;

        case CPU_INT_SYSTICK:                                   /* SysTick.                                             */
             CPU_CRITICAL_ENTER();
             CPU_REG_NVIC_ST_CTRL |= CPU_REG_NVIC_ST_CTRL_ENABLE;
             CPU_CRITICAL_EXIT();
             break;


                                                                /* ---------------- EXTERNAL INTERRUPT ---------------- */
        default:
            pos_max = CPU_INT_SRC_POS_MAX;
            if (pos < pos_max) {                                /* See Note #3.                                         */
                 group = (pos - 16) / 32;
                 nbr   = (pos - 16) % 32;

                 CPU_CRITICAL_ENTER();
                 CPU_REG_NVIC_SETEN(group) = DEF_BIT(nbr);
                 CPU_CRITICAL_EXIT();
             }
             break;
    }
}

/*$PAGE*/
/*
*********************************************************************************************************
*                                         CPU_IntSrcPendClr()
*
* Description : Clear a pending interrupt.
*
* Argument(s) : pos     Position of interrupt vector in interrupt table (see 'CPU_IntSrcDis()').
*
* Return(s)   : none.
*
* Caller(s)   : Application.
*
* Note(s)     : (1) See 'CPU_IntSrcDis()  Note #1'.
*
*               (2) The pending status of several interrupts cannot be clear/set :
*
*                   (a) Reset.
*                   (b) NMI.
*                   (c) Hard fault.
*                   (d) Memory Managment.
*                   (e) Bus Fault.
*                   (f) Usage Fault.
*                   (g) SVCall.
*                   (h) Debug monitor.
*                   (i) PendSV.
*                   (j) Systick 
*
*               (3) See 'CPU_IntSrcDis()  Note #3'.
*********************************************************************************************************
*/

void  CPU_IntSrcPendClr (CPU_INT08U  pos)

{
    CPU_INT08U  group;
    CPU_INT08U  nbr;
    CPU_INT08U  pos_max;
    CPU_SR_ALLOC();


    switch (pos) {
        case CPU_INT_STK_PTR:                                   /* ---------------- INVALID OR RESERVED --------------- */
        case CPU_INT_RSVD_07:
        case CPU_INT_RSVD_08:
        case CPU_INT_RSVD_09:
        case CPU_INT_RSVD_10:
        case CPU_INT_RSVD_13:
             break;
                                                                /* ----------------- SYSTEM EXCEPTIONS ---------------- */
        case CPU_INT_RESET:                                     /* Reset (see Note #2).                                 */
        case CPU_INT_NMI:                                       /* Non-maskable interrupt (see Note #2).                */
        case CPU_INT_HFAULT:                                    /* Hard fault (see Note #2).                            */
        case CPU_INT_MEM:                                       /* Memory management (see Note #2).                     */
        case CPU_INT_SVCALL:                                    /* SVCall (see Note #2).                                */
        case CPU_INT_DBGMON:                                    /* Debug monitor (see Note #2).                         */
        case CPU_INT_PENDSV:                                    /* PendSV (see Note #2).                                */
        case CPU_INT_BUSFAULT:                                  /* Bus fault.                                           */
        case CPU_INT_USAGEFAULT:                                /* Usage fault.                                         */
        case CPU_INT_SYSTICK:                                   /* SysTick.                                             */
             break;
                                                                /* ---------------- EXTERNAL INTERRUPT ---------------- */
        default:
            pos_max = CPU_INT_SRC_POS_MAX;
            if (pos < pos_max) {                                /* See Note #3.                                         */
                 group = (pos - 16) / 32;
                 nbr   = (pos - 16) % 32;

                 CPU_CRITICAL_ENTER();
                 CPU_REG_NVIC_CLRPEND(group) = DEF_BIT(nbr);
                 CPU_CRITICAL_EXIT();
             }
             break;
    }
}


/*$PAGE*/
/*
*********************************************************************************************************
*                                         CPU_IntSrcPrioSet()
*
* Description : Set priority of an interrupt source.
*
* Argument(s) : pos     Position of interrupt vector in interrupt table (see 'CPU_IntSrcDis()').
*
*               prio    Priority.  Use a lower priority number for a higher priority.
*
* Return(s)   : none.
*
* Caller(s)   : Application.
*
* Note(s)     : (1) See 'CPU_IntSrcDis()  Note #1'.
*
*               (2) Several interrupts priorities CANNOT be set :
*
*                   (a) Reset (always -3).
*                   (b) NMI (always -2).
*                   (c) Hard fault (always -1).
*
*               (3) See 'CPU_IntSrcDis()  Note #3'.
*********************************************************************************************************
*/

void  CPU_IntSrcPrioSet (CPU_INT08U  pos,
                         CPU_INT08U  prio)
{
    CPU_INT08U  group;
    CPU_INT08U  nbr;
    CPU_INT08U  pos_max;
    CPU_INT32U  prio_32;
    CPU_INT32U  temp;
    CPU_SR_ALLOC();


    prio_32 = CPU_RevBits((CPU_INT08U)prio);
    prio    = (CPU_INT08U)(prio_32 >> (3 * DEF_OCTET_NBR_BITS));

    switch (pos) {
        case CPU_INT_STK_PTR:                                   /* ---------------- INVALID OR RESERVED --------------- */
        case CPU_INT_RSVD_07:
        case CPU_INT_RSVD_08:
        case CPU_INT_RSVD_09:
        case CPU_INT_RSVD_10:
        case CPU_INT_RSVD_13:
             break;


                                                                /* ----------------- SYSTEM EXCEPTIONS ---------------- */
        case CPU_INT_RESET:                                     /* Reset (see Note #2).                                 */
        case CPU_INT_NMI:                                       /* Non-maskable interrupt (see Note #2).                */
        case CPU_INT_HFAULT:                                    /* Hard fault (see Note #2).                            */
             break;

        case CPU_INT_MEM:                                       /* Memory management.                                   */
             CPU_CRITICAL_ENTER();
             temp                 = CPU_REG_NVIC_SHPRI1;
             temp                &= ~(DEF_OCTET_MASK << (0 * DEF_OCTET_NBR_BITS));
             temp                |=  (prio           << (0 * DEF_OCTET_NBR_BITS));
             CPU_REG_NVIC_SHPRI1  = temp;
             CPU_CRITICAL_EXIT();
             break;

        case CPU_INT_BUSFAULT:                                  /* Bus fault.                                           */
             CPU_CRITICAL_ENTER();
             temp                 = CPU_REG_NVIC_SHPRI1;
             temp                &= ~(DEF_OCTET_MASK << (1 * DEF_OCTET_NBR_BITS));
             temp                |=  (prio           << (1 * DEF_OCTET_NBR_BITS));
             CPU_REG_NVIC_SHPRI1  = temp;
             CPU_CRITICAL_EXIT();
             break;

        case CPU_INT_USAGEFAULT:                                /* Usage fault.                                         */
             CPU_CRITICAL_ENTER();
             temp                 = CPU_REG_NVIC_SHPRI1;
             temp                &= ~(DEF_OCTET_MASK << (2 * DEF_OCTET_NBR_BITS));
             temp                |=  (prio           << (2 * DEF_OCTET_NBR_BITS));
             CPU_REG_NVIC_SHPRI1  = temp;
             CPU_CRITICAL_EXIT();
             break;

        case CPU_INT_SVCALL:                                    /* SVCall.                                              */
             CPU_CRITICAL_ENTER();
             temp                 = CPU_REG_NVIC_SHPRI2;
             temp                &= ~((CPU_INT32U)DEF_OCTET_MASK << (3 * DEF_OCTET_NBR_BITS));
             temp                |=  (prio                       << (3 * DEF_OCTET_NBR_BITS));
             CPU_REG_NVIC_SHPRI2  = temp;
             CPU_CRITICAL_EXIT();
             break;

        case CPU_INT_DBGMON:                                    /* Debug monitor.                                       */
             CPU_CRITICAL_ENTER();
             temp                = CPU_REG_NVIC_SHPRI3;
             temp                &= ~(DEF_OCTET_MASK << (0 * DEF_OCTET_NBR_BITS));
             temp                |=  (prio           << (0 * DEF_OCTET_NBR_BITS));
             CPU_REG_NVIC_SHPRI3  = temp;
             CPU_CRITICAL_EXIT();
             break;

        case CPU_INT_PENDSV:                                    /* PendSV.                                              */
             CPU_CRITICAL_ENTER();
             temp                 = CPU_REG_NVIC_SHPRI3;
             temp                &= ~(DEF_OCTET_MASK << (2 * DEF_OCTET_NBR_BITS));
             temp                |=  (prio           << (2 * DEF_OCTET_NBR_BITS));
             CPU_REG_NVIC_SHPRI3  = temp;
             CPU_CRITICAL_EXIT();
             break;

        case CPU_INT_SYSTICK:                                   /* SysTick.                                             */
             CPU_CRITICAL_ENTER();
             temp                 = CPU_REG_NVIC_SHPRI3;
             temp                &= ~((CPU_INT32U)DEF_OCTET_MASK << (3 * DEF_OCTET_NBR_BITS));
             temp                |=  (prio                       << (3 * DEF_OCTET_NBR_BITS));
             CPU_REG_NVIC_SHPRI3  = temp;
             CPU_CRITICAL_EXIT();
             break;


                                                                /* ---------------- EXTERNAL INTERRUPT ---------------- */
        default:
            pos_max = CPU_INT_SRC_POS_MAX;
            if (pos < pos_max) {                                /* See Note #3.                                         */
                 group                    = (pos - 16) / 4;
                 nbr                      = (pos - 16) % 4;

                 CPU_CRITICAL_ENTER();
                 temp                     = CPU_REG_NVIC_PRIO(group);
                 temp                    &= ~(DEF_OCTET_MASK << (nbr * DEF_OCTET_NBR_BITS));
                 temp                    |=  (prio           << (nbr * DEF_OCTET_NBR_BITS));
                 CPU_REG_NVIC_PRIO(group) = temp;
                 CPU_CRITICAL_EXIT();
             }
             break;
    }
}


/*$PAGE*/
/*
*********************************************************************************************************
*                                         CPU_IntSrcPrioGet()
*
* Description : Get priority of an interrupt source.
*
* Argument(s) : pos     Position of interrupt vector in interrupt table (see 'CPU_IntSrcDis()').
*
* Return(s)   : Priority of interrupt source.  If the interrupt source specified is invalid, then
*               DEF_INT_16S_MIN_VAL is returned.
*
* Caller(s)   : Application.
*
* Note(s)     : (1) See 'CPU_IntSrcDis()      Note #1'.
*
*               (2) See 'CPU_IntSrcPrioSet()  Note #2'.
*
*               (3) See 'CPU_IntSrcDis()      Note #3'.
*********************************************************************************************************
*/

CPU_INT16S  CPU_IntSrcPrioGet (CPU_INT08U  pos)
{
    CPU_INT08U  group;
    CPU_INT08U  nbr;
    CPU_INT08U  pos_max;
    CPU_INT16S  prio;
    CPU_INT32U  prio_32;
    CPU_INT32U  temp;
    CPU_SR_ALLOC();


    switch (pos) {
        case CPU_INT_STK_PTR:                                   /* ---------------- INVALID OR RESERVED --------------- */
        case CPU_INT_RSVD_07:
        case CPU_INT_RSVD_08:
        case CPU_INT_RSVD_09:
        case CPU_INT_RSVD_10:
        case CPU_INT_RSVD_13:
             prio = DEF_INT_16S_MIN_VAL;
             break;


                                                                /* ----------------- SYSTEM EXCEPTIONS ---------------- */
        case CPU_INT_RESET:                                     /* Reset (see Note #2).                                 */
             prio = -3;
             break;

        case CPU_INT_NMI:                                       /* Non-maskable interrupt (see Note #2).                */
             prio = -2;
             break;

        case CPU_INT_HFAULT:                                    /* Hard fault (see Note #2).                            */
             prio = -1;
             break;


        case CPU_INT_MEM:                                       /* Memory management.                                   */
             CPU_CRITICAL_ENTER();
             temp = CPU_REG_NVIC_SHPRI1;
             prio = (temp >> (0 * DEF_OCTET_NBR_BITS)) & DEF_OCTET_MASK;
             CPU_CRITICAL_EXIT();
             break;


        case CPU_INT_BUSFAULT:                                  /* Bus fault.                                           */
             CPU_CRITICAL_ENTER();
             temp = CPU_REG_NVIC_SHPRI1;
             prio = (temp >> (1 * DEF_OCTET_NBR_BITS)) & DEF_OCTET_MASK;
             CPU_CRITICAL_EXIT();
             break;


        case CPU_INT_USAGEFAULT:                                /* Usage fault.                                         */
             CPU_CRITICAL_ENTER();
             temp = CPU_REG_NVIC_SHPRI1;
             prio = (temp >> (2 * DEF_OCTET_NBR_BITS)) & DEF_OCTET_MASK;
             break;

        case CPU_INT_SVCALL:                                    /* SVCall.                                              */
             CPU_CRITICAL_ENTER();
             temp = CPU_REG_NVIC_SHPRI2;
             prio = (temp >> (3 * DEF_OCTET_NBR_BITS)) & DEF_OCTET_MASK;
             CPU_CRITICAL_EXIT();
             break;

        case CPU_INT_DBGMON:                                    /* Debug monitor.                                       */
             CPU_CRITICAL_ENTER();
             temp = CPU_REG_NVIC_SHPRI3;
             prio = (temp >> (0 * DEF_OCTET_NBR_BITS)) & DEF_OCTET_MASK;
             CPU_CRITICAL_EXIT();
             break;

        case CPU_INT_PENDSV:                                    /* PendSV.                                              */
             CPU_CRITICAL_ENTER();
             temp = CPU_REG_NVIC_SHPRI3;
             prio = (temp >> (2 * DEF_OCTET_NBR_BITS)) & DEF_OCTET_MASK;
             CPU_CRITICAL_EXIT();
             break;

        case CPU_INT_SYSTICK:                                   /* SysTick.                                             */
             CPU_CRITICAL_ENTER();
             temp = CPU_REG_NVIC_SHPRI3;
             prio = (temp >> (3 * DEF_OCTET_NBR_BITS)) & DEF_OCTET_MASK;
             CPU_CRITICAL_EXIT();
             break;


                                                                /* ---------------- EXTERNAL INTERRUPT ---------------- */
        default:
            pos_max = CPU_INT_SRC_POS_MAX;
            if (pos < pos_max) {                                /* See Note #3.                                         */
                 group = (pos - 16) / 4;
                 nbr   = (pos - 16) % 4;

                 CPU_CRITICAL_ENTER();
                 temp  = CPU_REG_NVIC_PRIO(group);
                 CPU_CRITICAL_EXIT();

                 prio  = (temp >> (nbr * DEF_OCTET_NBR_BITS)) & DEF_OCTET_MASK;
             } else {
                 prio  = DEF_INT_16S_MIN_VAL;
             }
             break;
    }

    if (prio >= 0) {
        prio_32 = CPU_RevBits((CPU_INT32U)prio);
        prio    = (CPU_INT16S)(prio_32 >> (3 * DEF_OCTET_NBR_BITS));
    }

    return (prio);
}