RandomNumberGen.c

/*****************************************************************************
 *                                                                           *
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 *       ************                                                        *
 *      ***        ***                                                       *
 *      ***   +++   ***                                                      *
 *      ***   + +   ***                                                      *
 *      ***   +                            CHIPCON CC1010                    *
 *      ***   + +   ***                 HAL - RandomNumberGen                *
 *      ***   +++   ***                                                      *
 *      ***       ***                                                        *
 *       ***********                                                         *
 *        *********                                                          *
 *                                                                           *
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 *                                                                           *
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 * Author:              ROH                                                  *
 *****************************************************************************
 * Revision history:                                                         *
 *                                                                           *
 * $Log: RandomNumberGen.c,v $
 * Revision 1.1  2002/10/14 13:04:33  tos
 * Initial version in CVS.
 *
 *                                                                           *
 ****************************************************************************/

#include <chipcon/hal.h>

//----------------------------------------------------------------------------
// halRandomNumberGen(...);
//
//  Description:
//      This function activates the true RNG in the CC1010, waits long enough
//      for the output to be truly random and then samples individual random
//      bits with a period which ensures that the output is sufficiently
//      random. This function must never be used at the same time as RF is
//      in use.
//      A total of _length_ bytes of random data is stored at the location
//      pointed to by _rnd_data_.
//
//  Arguments:
//      byte* rnd_data
//          A pointer to a buffer to receive the random bytes.
//      word length
//          The number of random bytes to generate.
//
//  Return value:
//      void
//----------------------------------------------------------------------------
void halRandomNumberGen(byte* rnd_data, word length) {
    byte b;
    int i;

    //Torgeir    
    //RANCON=0x10;            // Enable random number generation
    RANCON = 0x02;          // Enable random number generation
    RX_PD=0;                // Turn on receive chain

    for (i=20; i; i--);  // Wait for input to stabilize
    
    while (length--) {
        b=0;
        for (i=8; i; i--)
            b=(b<<1)|(RANCON&0x01);
        *rnd_data++=b;
    }
    
    RANCON=0;               // Disable random number generation
    RX_PD=1;                // Turn off receive chain    
}

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