急急急 求高手解答
我将process（a) 改成process(a,b) 在波形图里设置了b恒为0，为什么波形图会发生如此大的变化。b不变不是没影响吗？求解答啊 这个困扰了我2天的问题 以下为源程序，没改之前波形相当正常Library IEEE;
Use IEEE.STD_LOGIC_1164.ALL;
entity shouhj is
port
(
-- Input ports
a,b : instd_logic;
-- Output ports
x,y,z : out std_logic
);
end shouhj;
architecture arch of shouhj is
TYPE all_state IS(s0,s1,s2,s3,s4);
SIGNAL state:all_state;
-- Declarations (optional)
begin
p1:PROCESS(a)
BEGIN
IF (a='1' ) THEN
CASE state IS
WHEN s0=> state<=s1;
WHEN s1=> state<=s2;
WHEN s2=> state<=s3;
WHEN s3=> state<=s4;
WHEN s4=> state<=s0;
WHEN OTHERS=> NULL;
end case;
end if;
end process p1;
p2:PROCESS(state)
begin
CASE state IS
WHEN s0=> x<='0';y<='0';z<='0';
WHEN s1=> x<='1';y<='1';z<='0';
WHEN s2=> x<='1';y<='0';z<='0';
WHEN s3=> x<='1';y<='1';z<='0';
WHEN s4=> x<='1';y<='1';z<='1';
WHEN OTHERS=> NULL;
end case;
end process p2;
end arch;
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