Отправлено SM 04 февраля 2003 г. 21:03 В ответ на: Насчет деления 16бит на 16 бит. отправлено Summer2003 04 февраля 2003 г. 19:52

несмотря на немеренную с виду навороченность реализуется в ДСП в несколько команд.

/*___________________________________________________________________________
 |                                                                           |
 |   Function Name : div_s                                                   |
 |                                                                           |
 |   Purpose :                                                               |
 |                                                                           |
 |   Produces a result which is the fractional integer division of var1 by  |
 |   var2; var1 and var2 must be positive and var2 must be greater or equal  |
 |   to var1; the result is positive (leading bit equal to 0) and truncated  |
 |   to 16 bits.                                                             |
 |   If var1 = var2 then div(var1,var2) = 32767.                             |
 |                                                                           |
 |   Complexity weight : 18                                                  |
 |                                                                           |
 |   Inputs :                                                                |
 |                                                                           |
 |    var1                                                                   |
 |             16 bit short signed integer (Word16) whose value falls in the |
 |             range : 0x0000 0000 <= var1 <= var2 and var2 != 0.            |
 |                                                                           |
 |    var2                                                                   |
 |             16 bit short signed integer (Word16) whose value falls in the |
 |             range : var1 <= var2 <= 0x0000 7fff and var2 != 0.            |
 |                                                                           |
 |   Outputs :                                                               |
 |                                                                           |
 |    none                                                                   |
 |                                                                           |
 |   Return Value :                                                          |
 |                                                                           |
 |    var_out                                                                |
 |             16 bit short signed integer (Word16) whose value falls in the |
 |             range : 0x0000 0000 <= var_out <= 0x0000 7fff.                |
 |             It's a Q15 value (point between b15 and b14).                 |
 |___________________________________________________________________________|
*/
Word16 div_s(Word16 var1, Word16 var2)
{
    Word16 var_out = (Word16)0;
    Word16 iteration;
    Word32 L_num;
    Word32 L_denom;
    if ((var1 > var2) || (var1 < (Word16)0) || (var2 < (Word16)0)) {
        printf("Division Error\n");
        exit(0);
    }
    if (var2 == (Word16)0) {
        printf("Division by 0, Fatal error \n");
        exit(0);
    }
    if (var1 == (Word16)0) {
        var_out = (Word16)0;
    }
    else {
        if (var1 == var2) {
            var_out = MAX_16;
        }
        else {
            L_num = L_deposit_l(var1);
            L_denom = L_deposit_l(var2);
            for(iteration=(Word16)0; iteration< (Word16)15;iteration++) {
                var_out <<=1;
                L_num <<= 1;
                if (L_num >= L_denom) {
                    L_num = L_sub(L_num,L_denom);
                    var_out = add(var_out, (Word16)1);
                }
            }
        }
    }
    return(var_out);
}
Word32 L_deposit_l(Word16 var1)
{
    Word32 L_var_out;
    L_var_out = (Word32) var1;
    return(L_var_out);
}
Word32 L_sub(Word32 L_var1, Word32 L_var2)
{
    Word32 L_var_out;
    L_var_out = L_var1 - L_var2;
    if (((L_var1 ^ L_var2) & MIN_32) != 0L) {
        if ((L_var_out ^ L_var1) & MIN_32) {
            L_var_out = (L_var1 < 0L) ? MIN_32 : MAX_32;
            Overflow = 1;
        }
    }
    return(L_var_out);
}
Word16 add(Word16 var1,Word16 var2)
{
    Word16 var_out;
    Word32 L_somme;
    L_somme = (Word32) var1 + (Word32) var2;
    var_out = sature(L_somme);
    return(var_out);
}
Word16 sature(Word32 L_var1)
{
    Word16 var_out;
    if (L_var1 > 0X00007fffL) {
        Overflow = 1;
        var_out = MAX_16;
    }
    else {
        if (L_var1 < (Word32)0xffff8000L) {
            Overflow = 1;
            var_out = MIN_16;
        }
        else {
            Overflow = 0;
            var_out = extract_l(L_var1);
        }
    }
    return(var_out);
}
Word16 extract_l(Word32 L_var1)
{
    Word16 var_out;
    var_out = (Word16) L_var1;
    return(var_out);
}