17.3.3計(jì)數(shù)器I - 集成同步加法計(jì)數(shù)器

7.6計(jì)數(shù)器計(jì)數(shù)器功能清零、置數(shù)、保持和計(jì)數(shù)計(jì)數(shù)器分類(lèi)按時(shí)鐘控制同步計(jì)數(shù)器、異步計(jì)數(shù)器按計(jì)數(shù)過(guò)程加法計(jì)數(shù)器、減法計(jì)數(shù)器、加/減計(jì)數(shù)器(可逆計(jì)數(shù)器)按計(jì)數(shù)進(jìn)制二進(jìn)制計(jì)數(shù)器、十進(jìn)制計(jì)數(shù)器、任意進(jìn)制計(jì)數(shù)器計(jì)數(shù):記憶輸入時(shí)鐘脈沖個(gè)數(shù)的操作；計(jì)數(shù)器:能實(shí)現(xiàn)計(jì)數(shù)操作的電子電路；計(jì)數(shù)器的模:累計(jì)輸入脈沖的最大數(shù)目稱(chēng)為計(jì)數(shù)器容量、計(jì)數(shù)長(zhǎng)度，也稱(chēng)為計(jì)數(shù)器的模。計(jì)數(shù)器應(yīng)用：計(jì)數(shù)、定時(shí)和分頻等。7.6.1集成同步加法計(jì)數(shù)器7.6.1.174LS160/161和74LS162/163型

號(hào)計(jì)數(shù)進(jìn)制碼

制清零方式置數(shù)方式74LS160十進(jìn)制8421BCD碼異步清零同步置數(shù)74LS161十六進(jìn)制4位二進(jìn)制碼異步清零同步置數(shù)74LS162十進(jìn)制8421BCD碼同步清零同步置數(shù)74LS163十六進(jìn)制4位二進(jìn)制碼同步清零同步置數(shù)異步清零同步置數(shù)74LS160/161的功能表7.6.1.174LS160/161和74LS162/16374LS162/163的功能表同步清零同步置數(shù)7.6.1.174LS160/161和74LS162/1637.6.1.2計(jì)數(shù)器的級(jí)聯(lián)1.同步并行進(jìn)位方式100000000100100001000000010用74LS160構(gòu)成的千進(jìn)制加法計(jì)數(shù)器‘個(gè)位’‘十位’‘百位’RCO1.同步并行進(jìn)位方式同步4096進(jìn)制加法計(jì)數(shù)器7.6.1.2計(jì)數(shù)器的級(jí)聯(lián)2.異步串行進(jìn)位方式由74LS160構(gòu)成的百進(jìn)制加法計(jì)數(shù)器低位高位進(jìn)位7.6.1.2計(jì)數(shù)器的級(jí)聯(lián)7.6.1.3計(jì)數(shù)器進(jìn)制的改變N進(jìn)制計(jì)數(shù)器M進(jìn)制計(jì)數(shù)器？對(duì)于集成同步加法計(jì)數(shù)器74LS160/161和74LS162/163可利用清零法、置數(shù)法改變計(jì)數(shù)進(jìn)制。1.清零法(同步清零、異步清零)以N=16(1111)、M=12(1100)為例M異步清零M=12(1100)同步清零M-1=11(1011)(1)異步清零法Y7.6.1.3計(jì)數(shù)器進(jìn)制的改變(2)同步清零法Y7.6.1.3計(jì)數(shù)器進(jìn)制的改變2.置數(shù)法

預(yù)置數(shù)固定的十進(jìn)制加法計(jì)數(shù)器預(yù)置數(shù)可變的十進(jìn)制加法計(jì)數(shù)器7.6.1.3計(jì)數(shù)器進(jìn)制的改變2.置數(shù)法

【例7.6.1】由2片74LS161組成的同步加法計(jì)數(shù)器如圖所示。1.試分析其輸出Q的頻率與CP的頻率之間的關(guān)系？2.試用2片74LS161組成模為91的計(jì)數(shù)器，要求2片間采用同步并行進(jìn)位方式，并工作可靠。7.6.1.3計(jì)數(shù)器進(jìn)制的改變010011100014151001101111110100000011111111110010011007.6.1.3計(jì)數(shù)器進(jìn)制的改變1001CPRCO1RCO200(1)D觸發(fā)器的時(shí)鐘信號(hào)頻率是輸入時(shí)鐘CP的1/100。再經(jīng)由D觸發(fā)器組成的觸發(fā)器2分頻后，電路輸出Q的頻率是輸入時(shí)鐘CP頻率的1/200。解:7.6.1.3計(jì)數(shù)器進(jìn)制的改變(2)將2片74LS161計(jì)數(shù)器串接成模為16×16=256的計(jì)數(shù)器，當(dāng)計(jì)數(shù)器從