1、若干常用的組合邏輯電路若干常用的組合邏輯電路一、編碼器01010101001100110100000000100000100000000001000000001000000011110000000100000010000001000I1I2I3I4I6I5I7I0Y2Y1Y輸輸 入入輸輸 出出3位二進(jìn)制編碼器的真值表位二進(jìn)制編碼器的真值表2012345670123456701234567012345671012345670123456701234567012345670YI I I I I I I II I I I I I I II I I I I I I II I I I I I I IYI

2、 I I I I I I II I I I I I I II I I I I I I II I I I I I I IY 01234567012345670123456701234567I I I I I I I II I I I I I I II I I I I I I II I I I I I I I 0I1I2I3I4I5I6I7I8線線 - 3線編碼器線編碼器0Y1Y2Y3位二進(jìn)制（位二進(jìn)制（8線線3線）線）編碼器的框圖編碼器的框圖 753107632176542IIIIYIIIIYIIIIY2Y1Y0Y1I2I3I4I5I6I7I低電平實(shí)例：74HC148選通信號(hào))()()(SIII

3、IIIIIIIYSIIIIIIIIYSIIIIY6421643567054234567145672)(45672IIIIY選通信號(hào))(SIIIIY456720S1S附加輸出信號(hào))()()(SIIIIIIIISSIIIIIIIIYSIIIIIIIIYEXS012345670123456701234567為0時(shí)，電路工作無編碼輸入為0時(shí)，電路工作有編碼輸入輸 入輸 出1XXXXXXXX11111011111111111010XXXXXXX0000100XXXXXX01001100XXXXX011010100XXXX0111011100XXX01111100100XX011111101100X011

4、1111110100011111111111076543210IIIIIIIIS012YYYEXSYY的優(yōu)先權(quán)最高，的優(yōu)先權(quán)最高， 的優(yōu)先的優(yōu)先權(quán)權(quán)最低。最低。 7I0I狀態(tài)11不工作01工作，但無輸入10工作，且有輸入00不可能出現(xiàn)附加輸出信號(hào)的狀態(tài)及含意EXSYYEXY2Y1Y0Y7I6I5I4I3I2I1I0ISSY74HC14874HC148的框圖的框圖第一片的第一片的 作為輸出編碼的第作為輸出編碼的第4 4位位 EXY015AA0A15ASY S15A14A13A12A11A10A9A8A7A6A5A4A3A2A1A0AEXY2Y1Y0Y7I6I5I4I3I2I1I0ISSY74LS

5、148EXY2Y1Y0Y7I6I5I4I3I2I1I0ISSY74LS1483G3Z0G0Z2G2Z1G1Z2譯碼器一、二進(jìn)制譯碼器譯碼輸入：譯碼輸入：n位位二進(jìn)制二進(jìn)制代碼代碼譯碼輸出：譯碼輸出：m位輸出信號(hào)位輸出信號(hào)(高低電平高低電平)m=2n譯碼規(guī)則：對(duì)應(yīng)輸入的譯碼規(guī)則：對(duì)應(yīng)輸入的一組二進(jìn)制代碼一組二進(jìn)制代碼有且僅有一個(gè)輸有且僅有一個(gè)輸出端為有效電平，其余輸出端為相反電平出端為有效電平，其余輸出端為相反電平3線線- 8線譯碼器線譯碼器2A1A0A0Y1Y2Y3Y4Y5Y6Y7Y3位二進(jìn)制（位二進(jìn)制（3線線 8線）譯碼器的框圖線）譯碼器的框圖用二極管與門陣列組成的用二極管與門陣列組成的3線

6、線 8線譯碼器。線譯碼器。2A1A0ACCV2Y0Y1Y3Y4Y5Y6Y7Y用二極管與門陣列組成的用二極管與門陣列組成的3線線 8線譯碼器。線譯碼器。2A1A0ACCV2Y0Y1Y3Y4Y5Y6Y7Y用二極管與門陣列組成的用二極管與門陣列組成的3線線 8線譯碼器。線譯碼器。2A1A0ACCV2Y0Y1Y3Y4Y5Y6Y7Y用二極管與門陣列組成的用二極管與門陣列組成的3線線 8線譯碼器。線譯碼器。2A1A0ACCV2Y0Y1Y3Y4Y5Y6Y7Y用二極管與門陣列組成的用二極管與門陣列組成的3線線 8線譯碼器。線譯碼器。2A1A0ACCV2Y0Y1Y3Y4Y5Y6Y7Y用二極管與門陣列組成的用二極

7、管與門陣列組成的3線線 8線譯碼器。線譯碼器。2A1A0ACCV2Y0Y1Y3Y4Y5Y6Y7Y用二極管與門陣列組成的用二極管與門陣列組成的3線線 8線譯碼器。線譯碼器。2A1A0ACCV2Y0Y1Y3Y4Y5Y6Y7Y用二極管與門陣列組成的用二極管與門陣列組成的3線線 8線譯碼器。線譯碼器。2A1A0ACCV2Y0Y1Y3Y4Y5Y6Y7Y10000000010000000011001101010101000011110000000100000010001000000001000000001000000001002A1A0A0Y2Y1Y輸輸 入入輸輸 出出3Y4Y5Y6Y7Y真值表 邏輯表達(dá)

8、式：70127201221012100120mAAAYmAAAYmAAAYmAAAY.用電路進(jìn)行實(shí)現(xiàn) 用二極管與門陣列組成的3線8線譯碼器0G1G2G3G4G5G6G0Y1Y2Y3Y4Y5Y6Y7YSSG1S0A1A2A2S3S用與非門組成的3線-8線譯碼器 74LS1387G02100()YA A Am 當(dāng)當(dāng)S=1時(shí)時(shí)12101()YA A Am 32103()YA A Am42104()YA A Am 52105()YA A Am62106()YA A Am 72107()YA A Am22102() YA A Am0G1G2G3G4G5G6G0Y1Y2Y3Y4Y5Y6Y7YSSG1S0A

9、1A2A2S3S用與非門組成的3線-8線譯碼器 74LS1387G111111111011111111010011001101010101000011111101111111111011111111111110111111110111111110111111110111112A1A0A0Y1Y輸輸 入入輸輸 出出3Y4Y5Y6Y7Y2Y0111111111000000001S23SS 032101321073210()()()ZD D D DZD D D DZD D D D 015Z Z7Y2Y1Y0Y1S2S3S74LS138（1）2A1A0A3YY4 5Y6Y0Z1Z2Z3Z4Z5Z6Z7

10、Z74LS138（2）8Z9Z10Z11Z12Z13Z14Z15Z0D1D2D3DV5用兩片用兩片74LS138接成的接成的4線線16線譯碼器線譯碼器7Y2Y1Y0Y3YY4 5Y6Y1S2S3S2A1A0A8321093210153210()()()ZD D D DZD D D DZD D D D 利用課本圖4.3.8圖解釋三、用譯碼器設(shè)計(jì)組合邏輯電路1. 基本原理3位二進(jìn)制譯碼器給出3變量的全部最小項(xiàng);n位二進(jìn)制譯碼器給出n變量的全部最小項(xiàng);任意函數(shù)將n位二進(jìn)制譯碼輸出的最小項(xiàng)組合起來，可獲得任何形式的輸入變量不大于n的組合函數(shù)imY1234ZACA BCAB CZBCA B CZA BA

11、B CZA BCB CABC 134562137323540247ZABCABCABCABCmmmmZABCABCABCmmmZABCABCABCmmmZABCABCABCABCmmmm 134562137323540247()()()() Zm m m mZmm mZm m mZm m m m1CBA7Y2S1S0A1A3S0Y1Y2Y3Y4Y5Y6Y74LS1382A1Z2Z3Z4Z054321109876，agbfecd10987654321PD.PD.54321109876，abcdefgPD.abcdefg1. 七段字符顯示器 3A0A1AdYeYbYcYfYgY2AaYagbfec

12、d10987654321PD.32103120() aYA A A AA AA A100101111100100023AA01AA000001111001111000(a)aY111110011100100023AA01AA0000011110011110(b)bY31210210()bYA AA A AA A A32210() cYA AA A A110111011101010023AA01AA0000011110011110(c)cY100101101001111123AA01AA0000011110011110(d)dY210210210() dYA AAA AAA AA210()eYA

13、 AA3202110() fYA A AA AA A321210() gYA A AA A A100100000000111123AA01AA0000011110011110(e)eY111101110000011023AA01AA0000011110011110(f)fY011101111001111123AA01AA0000011110011110(g)gY3210312031210210322102102102102103202110321210()()()()()()() abcdefgYA A A AA AA AYA AA A AA A AYA AA A AYA A AA A AA

14、A AYA AAYA A AA AA AYA A AA A A3A3A0A1A2A2A1A0AaYfYeYgYbYcYdYCCVLTBI /RBORBIGND(7448)3210312031210210322102102102102103202110321210()()()()()()() abcdefgYA A A AA AA AYA AA A AA A AYA AA A AYA A AA A AA A AYA AAYA A AA AA AYA A AA A A3數(shù)據(jù)選擇器數(shù)據(jù)輸出數(shù)據(jù)輸出地址碼地址碼 多多路路數(shù)數(shù)據(jù)據(jù)輸輸入入究竟選擇哪一路數(shù)據(jù)輸出由究竟選擇哪一路數(shù)據(jù)輸出由A1、A0兩位地址

15、碼決定。兩位地址碼決定。數(shù)據(jù)選擇器數(shù)據(jù)選擇器4選選1數(shù)據(jù)選擇器數(shù)據(jù)選擇器 輸輸 入入輸輸 出出A1A0Y00110101D0D1D2D331001011021030iiiYA A DA A DA A DA A Dm DY4選1數(shù)據(jù)選擇器D0D1D2D3 A1 A0 真值表真值表 雙雙4選選1數(shù)據(jù)選擇器數(shù)據(jù)選擇器74LS153 MULTIPLEXER1C11GN1C02C02GN2C21C21C3BA2C12C31Y2Y74153inst8選選1數(shù)據(jù)選擇器數(shù)據(jù)選擇器74LS151 21002101210321022104210521062107FA A A DA A A DA A A DA A

16、A DA A A DA A A DA A A DA A A DMULTIPLEXERGNCBAD5D0D1D4D3D2D6D7YWN74151inst以雙以雙4 4選選1 1數(shù)據(jù)選擇器為例，說明工作原理。數(shù)據(jù)選擇器為例，說明工作原理。1Y2Y1A0A10D11D12D13D20D21D22D23D1S2STG1TG1TG1TG1TG1TG1TG1TG1TG1TG1TG1TG1雙雙4選選1數(shù)據(jù)選擇器數(shù)據(jù)選擇器74HC153110101110121013101()()()()YDA ADA ADA ADA AS 1Y1A0A10D11D12D13D1STG1TG1TG1TG1TG1TG1A1A0Y

17、11XX0000D10001D11010D12011D131SZR A GR AGRA GRAGRAG ()()() 1 ()ZR AGR AGR AGAG GAAA0101231DRDDRDAGR1YZS0A1A0D1D2D3D74HC15312例：用兩個(gè)“四選一”接成“八選一” “四選一”只有2位地址輸入，從四個(gè)輸入中選中一個(gè) “八選一”的八個(gè)數(shù)據(jù)需要3位地址代碼指定其中任何一個(gè)70126012501240123012201210120012DAAADAAADAAADAAADAAADAAADAAADAAAY)()()()()()()()(位地址輸入端作為第利用3SZA B CACA BC

18、02101210221032104210521062107210()()()()()()()() YDA A AD A A ADA A AD A A ADA A ADA A ADA A ADA A A1 ()0 ()0 () 1 ()0 () 1 ()0 () 1 () ZA B CACA BCA B CA B CA BCA BCAB CAB CABCABC解：解：8選選1數(shù)據(jù)選擇器邏輯函數(shù)式為：數(shù)據(jù)選擇器邏輯函數(shù)式為：0164217530 DDDDDDDDCABAAA 0120164217530 DDDDDDDDCABAAA 01213D20D21D22D23D2S4D5D6D7D0D1D2

19、D3D0A2A1A1A0AY2Y1Y2G1G74HC1531S10D11D12DCABZ011S 2S 四、加法器ABSCOCOSA BABABCOAB0011010101100001ABSCO輸輸 入入輸輸 出出ABSCOCI00001111A00110011B01010101S01101001CO00010111輸輸 入入輸輸 出出()SA B CIAB CIA BCIABCI 000011111000011110CIABSABSCOCOCICI雙全加器雙全加器74LS183的圖形符號(hào)的圖形符號(hào)011100101000011110CIABCO0()COA BB CIA CI 合并0求反二、多位加法器 串行進(jìn)位加法器 優(yōu)點(diǎn)：簡(jiǎn)單 缺點(diǎn)：慢2. 超前進(jìn)位加法器基本原理：加到第i位的進(jìn)位輸入信號(hào)是兩個(gè)加數(shù)第i位以前各位（0 j-1）的函數(shù)，可在相加前由A,B兩數(shù)確定。優(yōu)點(diǎn)：快，每1位的和及最后的進(jìn)位基本同時(shí)產(chǎn)生。 缺點(diǎn)：電路復(fù)雜。iiiiiiiiiiiiCIBABACOCIBASCOCI)()()()()(1進(jìn)位位直接