选一数据选择器VHDL源程序.doc

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1、LIBRARYIEEE;USEIEEE.STD_LOGIC_1164.ALL;ENTITYmux81ISPORT(A0,A1,A2,EN:INSTD_LOGIC;D:INSTD_LOGIC_VECTOR(7DOWNTO0);Y:OUTSTD_LOGIC);ENDENTITYmux81;ARCHITECTUREMUX1OFmux81ISSIGNALsel:STD_LOGIC_VECTOR(2DOWNTO0);BEGINsel<=A0&A1&A2;PROCESS(A0,A1,A2,sel,EN,D(0),D(1)

2、,D(2),D(3),D(4),D(5),D(6))BEGINIFEN='1'THENY<='0';ELSECASEselISWHEN"000"=>Y<=D(0);WHEN"001"=>Y<=D(1);WHEN"010"=>Y<=D(2);WHEN"011"=>Y<=D(3);WHEN"100"=>Y<=D(4);WHEN"101"=>Y<=D(5);WHEN"110"=>Y<=D(6);WHENOTHERS=>Y<='X';ENDCASE;ENDIF;ENDPROCESS;ENDMUX1;