MSP432 MCLK/SMCLK = 1:1 at 24 MHz

/* --COPYRIGHT--,BSD_EX
 * Copyright (c) 2013, Texas Instruments Incorporated
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * *  Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * *  Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * *  Neither the name of Texas Instruments Incorporated nor the names of
 *    its contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *******************************************************************************
 *
 *                       MSP432 CODE EXAMPLE DISCLAIMER
 *
 * MSP432 code examples are self-contained low-level programs that typically
 * demonstrate a single peripheral function or device feature in a highly
 * concise manner. For this the code may rely on the device's power-on default
 * register values and settings such as the clock configuration and care must
 * be taken when combining code from several examples to avoid potential side
 * effects. Also see http://www.ti.com/tool/mspdriverlib for an API functional
 * library & https://dev.ti.com/pinmux/ for a GUI approach to peripheral configuration.
 *
 * --/COPYRIGHT--*/
//******************************************************************************
//   MSP432P401 Demo - Device configuration for operation @ MCLK = DCO = 48MHz
//
//   Description: Proper device configuration to enable operation at MCLK=48MHz
//   including:
//   1. Configure VCORE level to 1
//   2. Configure flash wait-state to 1
//   3. Configure DCO frequency to 48MHz
//   4. Ensure MCLK is sourced by DCO
//
//   After configuration is complete, MCLK is output to port pin P4.3.
//
//                MSP432P401x
//             -----------------
//         /|\|                 |
//          | |                 |
//          --|RST              |
//            |             P4.3|----> MCLK
//            |                 |
//
//   William Goh
//   Texas Instruments Inc.
//   June 2016 (updated) | November 2013 (created)
//   Built with CCSv6.1, IAR, Keil, GCC
//******************************************************************************
#include "msp.h"
#include "stdint.h"


void error(void);

int main(void)
{
    volatile uint32_t i;
    uint32_t currentPowerState;

    WDT_A->CTL = WDT_A_CTL_PW |
                 WDT_A_CTL_HOLD;            // Stop WDT

    P1->DIR |= BIT0;                        // P1.0 set as output

    /* NOTE: This example assumes the default power state is AM0_LDO.
     * Refer to  msp432p401x_pcm_0x code examples for more complete PCM
     * operations to exercise various power state transitions between active
     * modes.
     */

    /* Step 1: Transition to VCORE Level 1: AM0_LDO --> AM1_LDO */

    /* Get current power state, if it's not AM0_LDO, error out */
    currentPowerState = PCM->CTL0 & PCM_CTL0_CPM_MASK;
    if (currentPowerState != PCM_CTL0_CPM_0)
        error();

    while ((PCM->CTL1 & PCM_CTL1_PMR_BUSY));
    PCM->CTL0 = PCM_CTL0_KEY_VAL | PCM_CTL0_AMR_1;
    while ((PCM->CTL1 & PCM_CTL1_PMR_BUSY));
    if (PCM->IFG & PCM_IFG_AM_INVALID_TR_IFG)
        error();                            // Error if transition was not successful
    if ((PCM->CTL0 & PCM_CTL0_CPM_MASK) != PCM_CTL0_CPM_1)
        error();                            // Error if device is not in AM1_LDO mode

    /* Step 2: Configure Flash wait-state to 1 for both banks 0 & 1 */
    FLCTL->BANK0_RDCTL = (FLCTL->BANK0_RDCTL & ~(FLCTL_BANK0_RDCTL_WAIT_MASK)) |
            FLCTL_BANK0_RDCTL_WAIT_1;
    FLCTL->BANK1_RDCTL  = (FLCTL->BANK0_RDCTL & ~(FLCTL_BANK1_RDCTL_WAIT_MASK)) |
            FLCTL_BANK1_RDCTL_WAIT_1;

    /* Step 3: Configure DCO to 48MHz, ensure MCLK uses DCO as source*/
//    CS->KEY = CS_KEY_VAL ;                  // Unlock CS module for register access
//    CS->CTL0 = 0;                           // Reset tuning parameters
//    CS->CTL0 = CS_CTL0_DCORSEL_5;           // Set DCO to 48MHz
//    /* Select MCLK = DCO, no divider */
//    CS->CTL1 = CS->CTL1 & ~(CS_CTL1_SELM_MASK | CS_CTL1_DIVM_MASK) |
//            CS_CTL1_SELM_3;
//    CS->KEY = 0; // Lock CS module from unintended accesses

    CS->KEY = CS_KEY_VAL;
//    CS->CTL0 = 0;                           // Reset tuning parameters
    CS->CTL0 = CS_CTL0_DCORSEL_4;    // Set DCO to 24MHz
    CS->CTL1 = (CS->CTL1 & ~(CS_CTL1_SELM_MASK | CS_CTL1_DIVM_MASK |
    		CS_CTL1_DIVHS_MASK | CS_CTL1_DIVS_MASK | CS_CTL1_SELS_MASK)) |
    				CS_CTL1_SELA__REFOCLK | CS_CTL1_SELS__DCOCLK |
					CS_CTL1_SELM__DCOCLK; // | CS_CTL1_DIVS__2 | CS_CTL1_DIVM__2;
    CS->KEY = 0;

    /* Step 4: Output MCLK to port pin to demonstrate 48MHz operation */
    P4->DIR |= BIT3;
    P4->SEL0 |=BIT3;                        // Output MCLK
    P4->SEL1 &= ~(BIT3);

    P7->DIR |= BIT0;
    P7->SEL0 |=BIT0;                        // Output SMCLK
    P7->SEL1 &= ~(BIT0);

    while (1)                               // continuous loop
    {
        P1->OUT ^= BIT0;                    // Blink P1.0 LED
        for (i = 200000; i > 0; i--);       // Delay
    }
}

void error(void)
{
    volatile uint32_t i;

    while (1)
    {
        P1->OUT ^= BIT0;
        for(i = 20000; i > 0; i--);           // Blink LED forever
    }
}