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ID:41295380
大小:1.33 MB
页数:45页
时间:2019-08-21
《VHDL双语教学第11章》由会员上传分享,免费在线阅读,更多相关内容在教育资源-天天文库。
1、VHDLSimulation&SynthesisBalanceofSignalDelayOptimizeofLateArrivedSignalLateArrivedSignalLateArrivedSignalMultiple‘IF’StatementLateArrivedSignalLateArrivedSignal(Improvement)所有能选通b的控制信号组合PriorityEncoded‘IF’ForLateArrivedSignalsEscapefromprevious2‘if’,butshou
2、ldbecaughtby‘z=b’selectionEndif;PriorityEncoded‘IF’ForLateArrivedControlSignalLateArrivedControlSignalA(1)A(2)A(3)A(4)A(5)A(6)zC(1)C(2)C(3)C(4)C(5)LateArrivedControlSignal(Improvement)A(1)A(2)A(3)A(4)A(5)A(6)z1C(1)C(2)C(3)C(5)C(4)A(4)z1zImprovedCodeLateArrivedS
3、ignalin‘CASE’Statement(contd.)ImprovedCode(Schematic)VHDLCodeBeforeOptimize(Case-WhenClasue)VHDLCodeAfterOptimize(Case-WhenClasue)MergeboththeCconditionandtheselconditionDelayin‘CASE’Statement(Schematic)Sel(0)Sel(1)Sel(2)ZDelayin‘CASE’Statement(Improvement)Se
4、l(0)0Sel(2)1Sel(1)Z1Z2ZDelayin‘CASE’StatementSel(1)isslowSel(1)=1Sel(1)=0ImprovedCodeClosetofinaloutputLongCalculationPathLongCalculationPath(Schematic)ImprovedCodeImprovedCode(Schematic)DecoderUsingIndexingIn1_intasindexIisindex,in1_intiscomparedinloop.Out1(i)
5、isaccessedbyvariableiDecoderUsingLoopDecoderUsingIndexingvs.‘Loop’MultipleInputsXORGateXORChains(Schematic)XORTreeXORTree(Schematic)MultiplexChainMultiplexChain(Schematic)MultiplexTreeOperatorinConditionalExpressionSchematicImprovedCodeImprovedCode(Schematic)Un
6、intentionalLatchData_inData_outCond_1UnnecessaryCalculationin‘LOOP’CodingStyleForSynthesis(1)OmitwaitforXXns;Omit(Q<=0afterXXns)UsingshifterregisterinsteadDQDQDQCodingStyleForSynthesis(2)OmitInitialValuesvariableSUM:INTEGER:=0;Usingpoweronset/resetsignalinstead
7、DQRSCodingStyleForSynthesis(3)DonotusevariablesforconstantsUseconstCodingStyleForSynthesis(4)IndentingYourCodesCodingStyleForSynthesis(5)Usestd_logic9valueAutomaticallyinitializedtoanunknownvalueEasytoperformaboard-levelsimulationCodingStyleForSynthesis(6)Donot
8、usebuffers
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