@Dcset - Don't Care Set
Syntax
@DCSET
Use
ABEL-HDL uses don't-care conditions to help in the optimization of partially-specified logic functions. Partially specified logic functions are those that have less than 2n significant input conditions, where n is the number of input signals. The @dcset option allows the optimization to use 1 or 0 for don't cares to optimize these functions.
?= and ?:= Assignment Operators