use WORK.fourpack.all;

entity t_buff_exmpl is
	port (a,b,c,d : in X01Z;	-- signals are four-valued
			f: out X01Z);
end t_buff_exmpl;

architecture t_buff_conc of t_buff_exmpl is
begin
	f <= a when b = '1' else 'Z';
	f <= c when d = '1' else 'Z';
end t_buff_conc;

architecture t_buff_bhv of t_buff_exmpl is
begin
	buff1: process (a,b)
	begin
		if (b='1') then
			f<=a;
		else 
			f<='Z';  --"drive" the output high Z when not enabled
		end if;
	end process buff1;

	buff2: process (c,d)
	begin
		if (d='1') then
			f<=c;
		else 
			f<='Z';  --"drive" the output high Z when not enabled
		end if;
	end process buff2;
end t_buff_bhv;