vhdl用两种并行语句实现四选一选择器
时间: 2023-10-10 08:08:39 浏览: 59
四选一选择器可以使用两种并行语句来实现:`if-else`语句和`case`语句。
使用`if-else`语句实现:
```vhdl
entity mux4to1_ifelse is
port(
data_in0, data_in1, data_in2, data_in3 : in std_logic_vector(7 downto 0);
sel : in std_logic_vector(1 downto 0);
data_out : out std_logic_vector(7 downto 0)
);
end mux4to1_ifelse;
architecture Behavioral of mux4to1_ifelse is
begin
process(sel, data_in0, data_in1, data_in2, data_in3)
begin
if sel = "00" then
data_out <= data_in0;
elsif sel = "01" then
data_out <= data_in1;
elsif sel = "10" then
data_out <= data_in2;
else
data_out <= data_in3;
end if;
end process;
end Behavioral;
```
使用`case`语句实现:
```vhdl
entity mux4to1_case is
port(
data_in0, data_in1, data_in2, data_in3 : in std_logic_vector(7 downto 0);
sel : in std_logic_vector(1 downto 0);
data_out : out std_logic_vector(7 downto 0)
);
end mux4to1_case;
architecture Behavioral of mux4to1_case is
begin
process(sel, data_in0, data_in1, data_in2, data_in3)
begin
case sel is
when "00" =>
data_out <= data_in0;
when "01" =>
data_out <= data_in1;
when "10" =>
data_out <= data_in2;
when others =>
data_out <= data_in3;
end case;
end process;
end Behavioral;
```