trng.c

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/******************************************************************************
*  Filename:       trng.c
*  Revised:        2016-06-30 09:21:03 +0200 (Thu, 30 Jun 2016)
*  Revision:       46799
*
*  Description:    Driver for the TRNG module
*
*  Copyright (c) 2015 - 2016, 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:
*
*  1) Redistributions of source code must retain the above copyright notice,
*     this list of conditions and the following disclaimer.
*
*  2) 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.
*
*  3) Neither the name of the ORGANIZATION 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
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******************************************************************************/

#include <driverlib/trng.h>

//*****************************************************************************
//
// Handle support for DriverLib in ROM:
// This section will undo prototype renaming made in the header file
//
//*****************************************************************************
#if !defined(DOXYGEN)
    #undef  TRNGConfigure
    #define TRNGConfigure                   NOROM_TRNGConfigure
    #undef  TRNGNumberGet
    #define TRNGNumberGet                   NOROM_TRNGNumberGet
#endif

//*****************************************************************************
//
//
//*****************************************************************************
void
TRNGConfigure(uint32_t ui32MinSamplesPerCycle,
              uint32_t ui32MaxSamplesPerCycle,
              uint32_t ui32ClocksPerSample)
{
    uint32_t ui32Val;

    //
    // Make sure the TRNG is disabled.
    //
    ui32Val = HWREG(TRNG_BASE + TRNG_O_CTL) & ~TRNG_CTL_TRNG_EN;
    HWREG(TRNG_BASE + TRNG_O_CTL) = ui32Val;

    //
    // Configure the startup number of samples.
    //
    ui32Val &= ~TRNG_CTL_STARTUP_CYCLES_M;
    ui32Val |= ((( ui32MaxSamplesPerCycle >> 8 ) << TRNG_CTL_STARTUP_CYCLES_S ) & TRNG_CTL_STARTUP_CYCLES_M );
    HWREG(TRNG_BASE + TRNG_O_CTL) = ui32Val;

    //
    // Configure the minimum and maximum number of samples pr generated number
    // and the number of clocks per sample.
    //
    HWREG(TRNG_BASE + TRNG_O_CFG0) = (
        ((( ui32MaxSamplesPerCycle >> 8 ) << TRNG_CFG0_MAX_REFILL_CYCLES_S ) & TRNG_CFG0_MAX_REFILL_CYCLES_M ) |
        ((( ui32ClocksPerSample         ) << TRNG_CFG0_SMPL_DIV_S          ) & TRNG_CFG0_SMPL_DIV_M          ) |
        ((( ui32MinSamplesPerCycle >> 6 ) << TRNG_CFG0_MIN_REFILL_CYCLES_S ) & TRNG_CFG0_MIN_REFILL_CYCLES_M )   );
}

//*****************************************************************************
//
//
//*****************************************************************************
uint32_t
TRNGNumberGet(uint32_t ui32Word)
{
    uint32_t ui32RandomNumber;

    //
    // Check the arguments.
    //
    ASSERT((ui32Word == TRNG_HI_WORD) ||
           (ui32Word == TRNG_LOW_WORD));

    //
    // Return the right requested part of the generated number.
    //
    if(ui32Word == TRNG_HI_WORD)
    {
        ui32RandomNumber = HWREG(TRNG_BASE + TRNG_O_OUT1);
    }
    else
    {
        ui32RandomNumber = HWREG(TRNG_BASE + TRNG_O_OUT0);
    }

    //
    // Initiate generation of new number.
    //
    HWREG(TRNG_BASE + TRNG_O_IRQFLAGCLR) = 0x1;

    //
    // Return the random number.
    //
    return ui32RandomNumber;
}