subdesign keyin
(
keyin  :INPUT;
CLK    :INPUT
keyout :OUTPUT;
)
variable
sm:MACHINE OF BITS(sb0)
         WITH STATES (s1=B"1",s0=B"0");
begin
sm.clk=clk;
table
sm,keyin=>sm;
s0,0=>s0;
s1,0=>s0;
s0,1=>s1;
s1,1=>s1;
end table;
keyout=!sb0;
end;