超大规模集成电路第九次作业2016秋-段成华.docx

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1、Assignment91.Designan8-bitupanddownsynchronouscounterinVHDLwiththefollowingfeatures:(1)Thesameportsareusedforsignalstobeinputtedandoutputted.Theportsarebi-directionallybuffered(three-state).(2)Thecounteriswithanasynchronousresetthatassignsaspecificin

2、itialvalueforcounting.(3)Thecounteriswithasynchronousdataloadcontrolinputforanewvalueofcountingandanenablecontrolinputforallowingtheupanddowncounting.Theloadcontrolinputhasapriorityovertheenablecontrolinput.Thisimpliesthatwhentheloadoperationisinproc

3、essthecounteroperationisprohibited.(4)Somedatatypes,suchasSTD_LOGIC,UNSIGNED,SIGNEDandINTEGER,maybeused.Synthesizethedesign.Createasetofreasonableinputwaveformsforyourdesignandcompletebothbehavioralandpost-place&routesimulationswithinternalsignalsand

4、/orvariablesincludedinwaveformorlistwindows.Solution:代码如下：libraryIEEE;useIEEE.STD_LOGIC_1164.ALL;useIEEE.STD_LOGIC_ARITH.ALL;useIEEE.STD_LOGIC_UNSIGNED.ALL;----Uncommentthefollowinglibrarydeclarationifinstantiating----anyXilinxprimitivesinthiscode.--

5、libraryUNISIM;--useUNISIM.VComponents.all;entitycount_8_bidirisPort(clk:inSTD_LOGIC;rst:inSTD_LOGIC;load:inSTD_LOGIC;enable:inSTD_LOGIC;cnt:inoutSTD_LOGIC_VECTOR(7downto0));endcount_8_bidir;architectureBehavioralofcount_8_bidirissignalcnt_in:STD_LOGI

6、C_VECTOR(7downto0);signalcnt_out:STD_LOGIC_VECTOR(7downto0);beginpro0:process(oe,cnt_out,cnt)beginif(load='1')thencnt<=(others=>'Z');cnt_in<=cnt;elsecnt<=cnt_out;endif;endprocess;pro1:process(clk,rst)beginif(rst='1')thencnt_out<=(others=>'0');elsifri

7、sing_edge(clk)thenif(load='1')thencnt_out<=cnt_in;elsif(enable='1')thencnt_out<=cnt_out+1;elsecnt_out<=cnt_out-1;endif;endif;endprocess;endBehavioral;解释代码：这里有两个进程，进程0时是用来控制三态门控制的双向端口。当cnt作为输入时（load='1'），把cnt赋给cnt_in（初值装载），然后置cnt为高阻状态；否则，即cnt作为输出时（loa

8、d='0'），把cnt_out（计数器计数输出值）赋给cnt。进程1的作用是：当复位信号rst='1'，计数器输出cnt_out为全0，否则在时钟的上升沿检测cnt端口是作为输入还是作为输出，当作为输入时（load='1'），把cnt_in中的数取进来，然后当up_down='0'时，进行加法运算，否则做减法运算，同时可以和进程0配合当load='0'，将数值从cnt_out输出到cnt。TestBench代码：LIBRARYieee;USEieee.std_logic_1164.ALL;USE