-1mux21a实体图3-【例3-1】ENTITYmux21aISPORT(a,b:INBIT;s:INBIT;y:OUTBIT);ENDENTITYmux21a;ARCHITECTUREoneOFmux21aISBEGINy<=aWHENs='0'ELSEb;ENDARCHITECTUREone;【例3-2】ENTITYmux21aISPORT(a,b,s:INBIT;y:OUTBIT);ENDENTITYmux21a;ARCHITECTUREoneOFmux21aISSIGNALd,e:BIT;BEGINd<=aAND(NOTS);e<=bANDs;y<=dORe;ENDARCHITECTUREone;【例3-3】ENTITYmux21aISPORT(a,b,s:INBIT;y:OUTBIT);ENDENTITYmux21a;ARCHITECTUREoneOFmux21aISBEGINPROCESS(a,b,s)BEGINIFs='0'THENy<=a;ELSEy<=b;ENDIF;ENDPROCESS;ENDARCHITECTUREone;-【例3-4】ENTITYe_nameISPORT(p_name:port_mdata_type;...p_namei:port_midata_type);ENDENTITYe_name;“IN”、“OUT”、“INOUT”、“BUFFER”【例3-5】ARCHITECTUREarch_nameOFe_nameIS[说明语句]BEGIN(功能描述语句)ENDARCHITECTUREarch_name;...--注意,a的数据类型必须是booleanIF(s1='0')AND(s2='1')OR(c<b+1)THEN..、BOOLEAN、STD_LOGICAND(与)、OR(或)、NAND(与非)、NOR(或非)、XOR(异或)、XNOR(同或)和NOT(取反)<=表达式WHEN赋值条件ELSE表达式WHEN赋值条件ELSE...表达式;z<=aWHENp1='1'ELSEbWHENp2='1'ELSEc;
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