我正在用VHDL编写一个完全基于真值表的2位4输入多路复用器。我使用了with-select语句 编码 . 然而,我得到以下错误信息。最后4行的错误信息. 我找不到任何语法错误,而且看其他with-select的例子,看起来和我的一模一样。我想我可能在分配向量值时犯了错误,但我找不到错误。软件是Quartus Prime Lite。
代码。
LIBRARY ieee;
use ieee.std_logic_1164.all;
entity tut43mux IS
PORT(
--sw: in Std_Logic_Vector(9 downto 0);
--LEDR: out Std_Logic_Vector(9 downto 0));
sw: in Std_Logic_Vector(0 to 9);
LEDR: out Std_Logic_Vector(0 to 9));
end tut43mux;
architecture behavior of tut43mux is
--signal s,u,v,w,x,t,y,m: Std_Logic_Vector(1 downto 0);
signal s,u,v,w,x,m: Std_Logic_Vector(0 to 1);
begin
LEDR(0)<=m(0);LEDR(1)<=m(1);
LEDR(2)<=sw(2);LEDR(3)<=sw(3);
LEDR(4)<=sw(4);LEDR(5)<=sw(5);
LEDR(6)<=sw(6);LEDR(7)<=sw(7);
LEDR(8)<=sw(8);LEDR(9)<=sw(9);
s(0)<=sw(0);s(1)<=sw(1);
u(0)<=sw(2);u(1)<=sw(3);
v(0)<=sw(4);v(1)<=sw(5);
w(0)<=sw(6);w(1)<=sw(7);
x(0)<=sw(8);x(1)<=sw(9);
with s select m
<= u when "00",
<= v when "01",
<= w when "10",
<= x when "11",
<= "00" when others;
end architecture behavior;
你只需要 <=
中的第一笔转让 with.. select
声明。其余的不需要。
with s select
m <= u when "00",
v when "01",
w when "10",
x when "11",
"00" when others;