超前进位加法器

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1、说明文档1•结构图:abcin>cout2•八段LED显示器的编码:DDP假设8段LED显示器是共阴极的,DP-G-F-E-D-C—B-A正好组成一个8位的数8seg,给这个数赋俏，即可以显示相应的数字。编码：显示字符字形井阳极共阴极dpgwfedcba字型码dpEwfedcba字形码0011000000COH001111113FH1111111001F9H0000011006HX10100100A4H010110115BH310110000BOH010011114FH441001100199H0110011066H■■1001001092H011011016DH66

2、1000001082H011111017DH7711111000F8H0000011107H881000000080H011111117FH991001000090H011011116FHAA1000100088H01110111刀HBB1000001183H011111007CHCC11000110C6H0011100139HDD10100001A1H010111105EHEE1000011086H0111100179HFF100011108EH0111000171H3.编码器子模块4到8位LED编码器modulecoder(in,out);input[3:O]in

3、;output[7:0]out;wire[3:0]in;reg[7:0]out;always@(in)begincase(in)4'hO:out=8'h3f;4'hl:out=8*h06;4'h2:out=8'h5b;4'h3:out=8'h4f;4'h4:out=8'h66;4'h5:out=8'h6d;4'h6:out=8'h7d;4'h7:out=8*h07;4'h&out=8'h7f;4'h9:out=8'h6f;4'ha:out=8'h77;4'hb:out=8'h7c;4'hc:out=8'h39;4'hd:out=8'h5e;4'he:out=8'h79

4、;4*hf:out=8'h71;endcaseendendmodule4.超前进位加法器子模块对一个4位全加器，第i位的两加数分别是Ai和Bi,进位输入信号是Ci-1,这个位产生的进位输出是Ci,则可以有得到：Ci二AiBi+（Ai+Bi）Ci-1令Gi二AiBi（进位产生函数）Pi=Ai+Bi（进位传递函数）则：Ci=Gi+PiCi-1所以有：CO二GO+POC-1C1二G1+P1COC2二G2+P2C1C3二G3+P3C2将上式逐次代入则可以得到如下表达式（C-1是最低位的进位输入）C0=G0+P0CTC1二G1+P1CO二G1+P1GO+P1POC-1C2二G2

5、+P2C1二G2+P2G1+P2P1C0二G2+P2G1+P2P1G0+P2P1POC-1C3二G3+P3C2二G3+P3G2+P3P2C1二G3+P3P2+P3P2C1二G3+P3P2+P3P2G1+P3P2P1CO二G3+P3P2+P3P2G1+P3P2P1GO+P3P2P1POC-1上述表达式说明只要各位数据和最低位进位同时输入，各位之间的进位信号与和就能同时产生。要据这样的原理可以实现超前进位加法器，这种加法器运算速度显著提高，但是复杂度也提高了。moduleadd4_head(a,b,cin,sum,cout);input[3:O]a;input[3:O]b

6、;inputcin;output[3:0]sum;outputcout;wire[3:0]p;wire[3:0]g;wire[3:0]t;wire[2:0]c;assignp[0]=a[0]

7、b[0];assignp[l]=a[l]

8、b[l];assignp[2]=a[2]

9、b[2];assignp[3]=a[3]

10、b[3];assignCO丄poj炉cin二go;assign21一H(pu」mCO」)-gE;assign22一H(p-2一炉c-l」)-gs;assigncoutHg【3二(p【3一20(竺2二§Q(gu二PE妙(go」-(po^cin)))))」as

11、signsumo」nto>cin;assignsumsHtE>cobassignsum【2一nts>CE;assignsumw一H>csjendmodu-eassignto=ao>borassigntEnaE>b〔lrassign=2一naE>bsjassign(sHas>S3一；assigngoJHao一炉b巨；assigngEHaE&.bE;assigngsHaE妙bE;assigngw一Hasmbw」；5•例化两个子模块把超前进位加法器和4到8位LED编码器两个模块例化放一起，完成本设计moduleadd_display(a,b,cin’cou