FUNCTIONS(3)

NAME

     overflow MDI_reciprocal, MDI_shift, ,MDI_mul, MDI_sqrt

     A set of functions emulating image-processor operations.

SYNOPSIS

     extern short MDI_mul(short x, short y);
     extern short MDI_reciprocal(short x);
     extern short MDI_shift(short x, int shift);
     extern short MDI_sqrt(short x);
     extern int overflow(int x);

DESCRIPTION

     These functions emulate some of the operations and functions
     implemented in the image processor.

     MDI_mul multiplies two 16-bit numbers,  returning  the  most
     significant 16 bits.

     MDI_reciprocal returns the value that would be obtained from
     a  reciprocal  table.   In  this case the table value is the
     result obtained with a dividend of 32768.  If the divisor is
     zero, zero is returned.

     MDI_shift performs an arithmetic shift on the first argument
     by  the amount specified by the second.  A positive shift is
     to the left, negative to the right.

     MDI_sqrt returns the value that would  be  obtained  from  a
     15-bit square-root table.  The numbers are treated as binary
     fractions with the binary point to the left, in other  words
     the  argument is treated as if it were normalized  by 32768.
     A negative argument, that is,  bit  15,  set  results  in  a
     return of -1.

     overflow is not actually an image-processor emulation  func-
     tion, but is used in the simulation as a check for excessive
     left shift in MDI_shift.

EXAMPLES

     See ~soi/(version)/src/libMDI.d/functions.c

HISTORY

     1994 June 13, Lyle Bacon, created for SOI v 0.9