Atmel ARM-Based Evaluation Kit AT91SAM9N12-EK AT91SAM9N12-EK Data Sheet

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SAM9N12/SAM9CN11/SAM9CN12 [DATASHEET]

11063K–ATARM–05-Nov-13

The sample code below gives a Berlekamp iterative procedure for finding the value of the error location polynomial.

The input of the procedure is the si[] table defined in the remainder substitution procedure.

The output of the procedure is the error location polynomial named smu (sigma mu). The polynomial coefficients belong
to the field. The smu[NB_ERROR+1][] is a table that contains all these coefficients.

NB_ERROR_MAX defines the maximum value of the error correcting capability.

NB_ERROR defines the error correcting capability selected at encoding/decoding time.

NB_FIELD_ELEMENTS defines the number of elements in the field.

int get_sigma()

{

int i;

int j;

int k;

/* mu          */

int mu[NB_ERROR_MAX+2];

/* sigma ro   */

int sro[2*NB_ERROR_MAX+1];

/* discrepancy */

int dmu[NB_ERROR_MAX+2];

/* delta order   */

int delta[NB_ERROR_MAX+2];

/* index of largest delta */

int ro;

int largest;

int diff;

/*                    */

/*     First Row      */

/*                    */

/* Mu */

mu[0]  = -1; /* Actually -1/2 */

/* Sigma(x) set to 1 */

for (i = 0; i < (2*NB_ERROR_MAX+1); i++)

smu[0][i] = 0;

smu[0][0] = 1;

/* discrepancy set to 1 */

dmu[0] = 1;

/* polynom order set to 0 */

lmu[0] = 0;

/* delta set to -1 */

delta[0]  = (mu[0] * 2 - lmu[0]) >> 1;

/*                     */

/*     Second Row      */

/*                     */

/* Mu */

mu[1]  = 0;

/* Sigma(x) set to 1 */

for (i = 0; i < (2*NB_ERROR_MAX+1); i++)

smu[1][i] = 0;

smu[1][0] = 1;

/* discrepancy set to Syndrome 1 */

dmu[1] = si[1];

/* polynom order set to 0 */

lmu[1] = 0;