数字逻辑第7讲编码器和译码器

1、college of computer science, swpucomputer sciencecomputer science数字逻辑数字逻辑 college of computer science, swpu数字逻辑数字逻辑 college of computer science, swpu数字逻辑数字逻辑 college of computer science, swpu2mn数字逻辑数字逻辑 college of computer science, swpu数字逻辑数字逻辑 college of computer science, swpu数字逻辑数字逻辑 college of co

2、mputer science, swpui0 i1 i2 i3 i4 i5 i6 i7y2 y1 y03 3位二进制编码器的真值表位二进制编码器的真值表1 0 0 0 0 0 0 0 0 0 00 1 0 0 0 0 0 0 0 0 10 0 1 0 0 0 0 0 0 1 00 0 0 1 0 0 0 0 0 1 10 0 0 0 1 0 0 0 1 0 00 0 0 0 0 1 0 0 1 0 10 0 0 0 0 0 1 0 1 1 00 0 0 0 0 0 0 1 1 1 1二进制二进制编码器编码器y0y1y2i0i1i72n个个输输入入n个个输输出出数字逻辑数字逻辑 college

3、of computer science, swpu20123 456701234 567012345 670123456 7 yii ii i i iiii ii i i iiii ii ii i iii ii ii i i数字逻辑数字逻辑 college of computer science, swpu数字逻辑数字逻辑 college of computer science, swpu245671236701357yiiiiyiiiiyiiii数字逻辑数字逻辑 college of computer science, swpu 数字逻辑数字逻辑 college of computer sc

4、ience, swpu45672yi i i i23671yi i i i13570yi i i i数字逻辑数字逻辑 college of computer science, swpu数字逻辑数字逻辑 college of computer science, swpu数字逻辑数字逻辑 college of computer science, swpu输 入i7 i6 i5 i4 i3 i2 i1 i0输 出y2 y1 y010 10 0 10 0 0 1 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 11 1 11 1 01 0 11 0

5、00 1 10 1 00 0 10 0 0数字逻辑数字逻辑 college of computer science, swpu12463465671234567345675677024534567234567345676771456745675676772iiiiiiiiiiiiiiiiiiiiiiiiiiyiiiiiiiiiiiiiiiiiiiiiiyiiiiiiiiiiiiiiy数字逻辑数字逻辑 college of computer science, swpu111111&1&y2 y1 y0i7 i6 i5 i4 i3 i2 i1 i08线线-3线线优优先先编编码码器器

6、数字逻辑数字逻辑 college of computer science, swpu思考思考：如果将输入和输出改为以低电平为有效信号，那么逻辑表达式是怎么样的呢？逻辑图呢？276541765 4 35 42076 564 3642 1yiiiiyiii i ii i iyii ii i ii i i i数字逻辑数字逻辑 college of computer science, swpu输输入入输输出出使能输出，用于级联使能输出，用于级联eo选通输出选通输出gs使能输入使能输入eiei_l有效有效有输入请求有输入请求gs_l有效有效ei_l有效有效没有输入请求没有输入请求eo_l有效有效数字逻辑

7、数字逻辑 college of computer science, swpu反相器反相器缓冲器缓冲器数字逻辑数字逻辑 college of computer science, swpua2a1a0gseoeii7i0a2a1a0gseoeii7i0q15_lq8_lq7_lq0_ly0y1y2y3gs2 2个个74x14874x148级联为级联为16164 4优先编码器优先编码器数字逻辑数字逻辑 college of computer science, swpu用用8-38-3优先编码器优先编码器74x14874x148级联为级联为64-664-6优先编码器优先编码器a2a1a0gseoeii

8、7i0片间优先级的编码片间优先级的编码 利用第利用第9 9片片74x14874x148 每片的每片的gsgs端接到第端接到第9 9片的输入端片的输入端 第第9 9片的输出作为高片的输出作为高3 3位（位（ra5ra5ra3ra3）片内优先级片内优先级片间优先级片间优先级 输出：输出：6 6位位低低3 3位位高高3 3位位8 8片输出片输出a2a2a0a0通过或门作为通过或门作为最终输出的低最终输出的低3 3位位ra2ra2ra0ra0数字逻辑数字逻辑 college of computer science, swpu分析判定优先级电路：（利用分析判定优先级电路：（利用74x148 74x148

9、 ） 8个个_电平有效输入电平有效输入i0_li7_l，_的优先级最高的优先级最高 地址输出地址输出a2a0，_电平有效电平有效 若输出若输出avalid高电平有效，则表示高电平有效，则表示_a2a1a0gseoei74x148i7i0i0_li7_la2a1a0avalid低低i0_l至少有一个输入有效至少有一个输入有效高高数字逻辑数字逻辑 college of computer science, swpu设计判定优先级电路：设计判定优先级电路：（利用（利用74x148 74x148 ） 8个输入个输入i0i7高电平有效，高电平有效，i7优先级最高优先级最高 地址输出地址输出a2a0，高电平

10、有效，高电平有效 如果没有输入有效，为如果没有输入有效，为111且输出且输出idle有效有效i7i0a2a1a0idlea2a1a0gseoeii7i074x148数字逻辑数字逻辑 college of computer science, swpu数字逻辑数字逻辑 college of computer science, swpu数字逻辑数字逻辑 college of computer science, swpu使能使能输入输入编码编码输出输出编码编码映射映射译码器（译码器（decoderdecoder）编码器（编码器（encoderencoder）n位二进制码位二进制码2n中取中取1码码使能

11、使能输入输入编码编码输出输出编码编码映射映射2n中取中取1码码n位二进制码位二进制码数字逻辑数字逻辑 college of computer science, swpu数字逻辑数字逻辑 college of computer science, swpu2-42-4译码器译码器y0y1y2y3a0a1en 0 x x 0 0 0 0 1 0 0 0 0 0 1 1 0 1 0 0 1 0 1 1 0 0 1 0 0 1 1 1 1 0 0 0输输 入入en a1 a2输输 出出 y3 y2 y1 y02-42-4二进制译码器真值表二进制译码器真值表数字逻辑数字逻辑 college of comp

12、uter science, swpu 0 x x 0 0 0 0 1 0 0 0 0 0 1 1 0 1 0 0 1 0 1 1 0 0 1 0 0 1 1 1 1 0 0 0输输 入入en a1 a2输输 出出 y3 y2 y1 y02-42-4二进制译码器真值表二进制译码器真值表y0 = en ( a1 a2 )y1 = en ( a1 a2 )y2 = en ( a1 a2 )y3 = en (a1 a2 )yi = en mi数字逻辑数字逻辑 college of computer science, swpu数字逻辑数字逻辑 college of computer science, s

13、wpuy0y1y2y3gab1/2 74x139y0y1y2y3gab1/2 74x139y0y1y2y3gab1/2 74x139g_laby0_ly1_ly2_ly3_l数字逻辑数字逻辑 college of computer science, swpua2 a1 a0 y0 y1 y2 y3 y4 y5 y6 y7 0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0

14、1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 真真值值表表数字逻辑数字逻辑 college of computer science, swpu01270126012501240123012201210120aaayaaayaaayaaayaaayaaayaaayaaay逻辑表达式逻辑表达式数字逻辑数字逻辑 college of computer science, swpu&111 a2 a1 a0 y7 y6 y5 y4 y3 y2 y1 y0逻逻辑辑图图3线线|8线线译译码码器器数字逻辑数字逻辑 college of computer science,

15、swpu数字逻辑数字逻辑 college of computer science, swpun0n1n2n3en_l+5vd0_ld7_ld8_ld15_l用用74x13874x138设计设计4-16译码器译码器思路：思路： 1616个输出需要个输出需要 片片74x13874x138？y0y7abcg1g2ag2by0y7abcg1g2ag2bu1u2 任何时刻只有任何时刻只有一片在工作。一片在工作。 4 4个输入中，个输入中，哪些位控制片选哪些位控制片选哪些位控制输入哪些位控制输入数字逻辑数字逻辑 college of computer science, swpu数字逻辑数字逻辑 colle

16、ge of computer science, swpuf = (x,y,z) (0,3,6,7) = (x,y,z) (1,2,4,5)对于二进制译码器：对于二进制译码器：yi = en mi 当使能端有效时，当使能端有效时，yi = mi对低电平有效输出：对低电平有效输出：yi_l = yi 当使能端有效时，当使能端有效时，yi_l = mi = miabcg1g2ag2by0y1y2y3y4y5y6y774x138数字逻辑数字逻辑 college of computer science, swpuzyxabcg1g2ag2by0y1y2y3y4y5y6y774x138f+5vf = (x

17、,y,z) (0,3,6,7)当使能端有效时当使能端有效时yi = mi数字逻辑数字逻辑 college of computer science, swpuzyxabcg1g2ag2by0y1y2y3y4y5y6y774x138+5vff = (x,y,z) (0,3,6,7)数字逻辑数字逻辑 college of computer science, swpu= m1 m2 m4 m5= m1 m2 m4 m5f = (x,y,z) ( 1, 2, 4, 5 )zyxabcg1g2ag2by0y1y2y3y4y5y6y774x138+5vf数字逻辑数字逻辑 college of compute

18、r science, swpuabcdefg dp公共阴极公共阴极abcdefgdp常用的有：常用的有：半导体数码管（半导体数码管（ledled）液晶数码管（液晶数码管（lcdlcd）abcdefg dp公共阳极公共阳极数字逻辑数字逻辑 college of computer science, swpuabcdefg111111011011010011111数字逻辑数字逻辑 college of computer science, swpu七七段段显显示示译译码码器器的的真真值值表表0 0 0 0 0 0 0 10 0 1 00 0 1 10 1 0 00 1 0 10 1 1 00 1 1

19、11 0 0 01 0 0 11 0 1 01 0 1 11 1 0 01 1 0 11 1 1 01 1 1 11 1 1 1 1 1 00 1 1 0 0 0 01 1 0 1 1 0 11 1 1 1 0 0 10 1 1 0 0 1 11 0 1 1 0 1 10 0 1 1 1 1 11 1 1 0 0 0 01 1 1 1 1 1 11 1 1 0 0 1 10 0 0 1 1 0 10 0 1 1 0 0 10 1 0 0 0 1 11 0 0 1 0 1 10 0 0 1 1 1 10 0 0 0 0 0 0a3 a2 a1 a0a b c d e f g01234567891

20、01112131415数字逻辑数字逻辑 college of computer science, swpubcd - 七段显示译码器的卡诺图七段显示译码器的卡诺图ya = a3a2a2a0 + a3a1 + a2a0yb = a3a1 + a2a1a0 + a2a1a0数字逻辑数字逻辑 college of computer science, swpubcd - 七段显示译码器的卡诺图七段显示译码器的卡诺图yc = a3a2 + a2a1a0yd = a2a1a0 + a2a1a0 + a2a1a0数字逻辑数字逻辑 college of computer science, swpubcd - 七段显示译码器的卡诺图七段显示译码器的卡诺图ye = a2a1 + a0yf = a3a2a0 + a1a0 + a2a1数字逻辑数字逻辑 college of computer science, swpubcd - 七段显示译码器的卡诺图七段显示译码器的卡诺图yg = a3a2a1 + a2a