DSPMAC

Summary:
The DSPMAC function is designed to be used in applications requiring a MAC that
can accumulate both positive and negative products (i.e. Z=C +/- X*Y).  The Add input
controls whether the positive or negative product is accumulated.  Note that
the accumulator and reset circuits must be supplied externally.  The width of the 
X and Y inputs can be controlled independently with the Xwidth and Ywidth parameters, 
respectively.  The formats (signed or unsigned) of X and Y are also controlled 
independently with XS and YS signals, respectively.  The formats of X and Y may 
be changed dynamically to accommodate extended precision calculations.  The multiplier 
is always Booth encoded.  

The output, Z, is has the same precision as the C input.  When rounding is 
selected (Round>0), only the bits of Z with indices from Round to Awidth-1 
are valid.

The type of the final adder type is controlled by "AdderType".

Function: 
    Z=C+X*Y (Add HIGH)
    Z=C-X*Y (Add LOW)

Signals:
    X: Xwidth wide input (XS sets format)
    Y: Ywidth wide input (YS sets format)
    Z: Cwidth wide output
    C: Cwidth wide accumulator input
    Add: HIGH to add X*Y, LOW to subtract X*Y
    XS: HIGH for X signed, LOW for unsigned
    YS: HIGH for Y signed, LOW for unsigned

Parameters:
    Name: actual module name
    Xwidth: width of input X
    Ywidth: width of input Y
    Cwidth: width of the accumulator input, output
    AdderType:  the type of the final adder ('fastcla', 'cla', 'clsa' or 'csa')
    Round: select the rounding position (0 for no rounding)
    AdderType: type of the adder to build (cla, fastcla, clsa, csa, ripple)

Verilog Usage:  
    Name(C,X,Y,Add,XS,YS,Z);

Version: $Id: DSPMAC.help,v 1.4 1998/08/22 00:28:40 peter Exp $