[第五章VHDL设计进阶1.ppt

LIBRARY IEEE; USE IEEE.STD_LOGIC_1164.ALL; USE IEEE.STD_LOGIC_UNSIGNED.ALL; ENTITY CNT IS PORT (CLK : IN STD_LOGIC; CQ : OUT STD_LOGIC_VECTOR(2 DOWNTO 0); COUT : OUT STD_LOGIC ); END CNT; ARCHITECTURE behav OF CNT IS BEGIN PROCESS(CLK) VARIABLE CQI : STD_LOGIC_VECTOR(2 DOWNTO 0); BEGIN if CLKEVENT AND CLK=1 THEN CQI := CQI + 1; END IF; IF CQI =111 THEN COUT = 1; ELSE COUT = 0; END IF; CQ = CQI; END PROCESS; END behav; Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 5.2.4 双向电路和三态控制电路设计 1 三态门设计 【例5-13】 LIBRARY IEEE; USE IEEE.STD_LOGIC_1164.ALL; ENTITY tri_s IS port ( enable : IN STD_LOGIC; datain : IN STD_LOGIC_VECTOR(7 DOWNTO 0); dataout : OUT STD_LOGIC_VECTOR(7 DOWNTO 0)); END tri_s ; ARCHITECTURE bhv OF tri_s IS BEGIN PROCESS(enable,datain) BEGIN IF enable = 1 THEN dataout = datain ; ELSE dataout =ZZZZZZZZ ; END IF ; END PROCESS; END bhv; Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 图5-12 8位3态控制门电路与仿真图 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 5.2.5 双向端口设计 【例5-14】 library ieee; use ieee.std_logic_1164.all; entity tri_state is port (control : in std_logic; in1: in std_logic_vector(7 downto 0); q : inout std_logic_vector(7 downto 0); x : out std_logic_vector(7 downto 0)); end tri_state; architecture body_tri of tri_state is begin process(control,q,in1) begin if (control = 0) then x = q ; else q = in1; x=ZZZZZZZZ ； end if; end process; end body_tri; Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyr