PPT 슬라이드
type bit is ( ‘0’, ‘1’ ) ;
type boolean is ( false, true ) ;
Type bit is helpful and concise for modeling hardware, but does not provide for high-impedance, unknown, don’t care, Etc.
Type boolean is useful for modeling at the more abstract level. All relational operations return a value of type boolean.
architecture BEHAVE of MUX is
signal A,B,Sel, Z : bit ;
begin if Sel = ‘1’ then Z <= A ; else Z <= B ; end if . . .
both yield boolean result