adder4.vhd

来自「一本很好的关于学习VHDL的书,Fundamentals of Digital 」· VHDL 代码 · 共 22 行

LIBRARY ieee ;
USE ieee.std_logic_1164.all ;
USE work.fulladd_package.all ;

ENTITY adder4 IS
	PORT ( 	Cin 			: IN 	STD_LOGIC ;
			x3, x2, x1, x0 	: IN 	STD_LOGIC ;
			y3, y2, y1, y0 	: IN 	STD_LOGIC ;
			s3, s2, s1, s0 	: OUT 	STD_LOGIC ;
			Cout 			: OUT 	STD_LOGIC ) ;
END adder4 ;

ARCHITECTURE Structure OF adder4 IS
	SIGNAL c1, c2, c3 : STD_LOGIC ;
BEGIN
	stage0: fulladd PORT MAP ( Cin, x0, y0, s0, c1 ) ;
	stage1: fulladd PORT MAP ( c1, x1, y1, s1, c2 ) ;
	stage2: fulladd PORT MAP ( c2, x2, y2, s2, c3 ) ;
	stage3: fulladd PORT MAP ( 
		Cin => c3, Cout => Cout, x => x3, y => y3, s => s3  ) ;
END Structure ;