用狀態(tài)機(jī)實(shí)現(xiàn)對ADC0809的采樣控制電路實(shí)現(xiàn)

1、用狀態(tài)機(jī)實(shí)現(xiàn)對ADC0809的采樣控制電路實(shí)現(xiàn)一、 實(shí)驗(yàn)?zāi)康?學(xué)習(xí)用狀態(tài)機(jī)實(shí)現(xiàn)對A/D轉(zhuǎn)換器ADC0809的采樣控制電路的實(shí)現(xiàn)二、 實(shí)驗(yàn)原理ADC0809是CMOS的8為A/D轉(zhuǎn)換器，片內(nèi)有8路模擬開關(guān)，可控制8個模擬量的一個進(jìn)入轉(zhuǎn)換器中。ADC0809的精度為8位，轉(zhuǎn)換時間約100s，含鎖存控制的8路多路開關(guān)，輸出有三態(tài)緩沖器控制，單5V電源供電。主要控制信號說明：START是轉(zhuǎn)換啟動信號，高電平有效；ALE是3為通道選擇地址（ADDC、ADDB、ADDA）信號的鎖存信號。當(dāng)模擬量送至某一輸入端（如IN1或IN2等），有3為地址信號選擇，而地址信號有ALE鎖存；EOC是轉(zhuǎn)換情況狀態(tài)信號（類似

2、于AD574的STATUS）,當(dāng)啟動轉(zhuǎn)換約100s后，EOC產(chǎn)生一個負(fù)脈沖，以示轉(zhuǎn)換結(jié)束；在EOC的上升沿后，若使輸出使能信號OE為高電平，則控制打開三態(tài)緩沖器，把轉(zhuǎn)換好的8位數(shù)據(jù)輸至數(shù)據(jù)總線。至此ADC0809的一次轉(zhuǎn)換結(jié)束。三、 實(shí)驗(yàn)過程程序代碼：LIBRARY IEEE;USE IEEE.STD_LOGIC_1164.ALL;ENTITY ADCINT ISPORT ( D:IN STD_LOGIC_VECTOR(7 DOWNTO 0); CLK,EOC:IN STD_LOGIC; LOCK1,ALE,START,OE,ADDA:OUT STD_LOGIC; Q:OUT STD_LOGI

3、C_VECTOR(7 DOWNTO 0);END ADCINT;ARCHITECTURE behav OF ADCINT ISTYPE states IS (st0,st1,st2,st3,st4,st5,st6);SIGNAL current_state,next_state: states:=st0;SIGNAL REGL :STD_LOGIC_VECTOR(7 DOWNTO 0);SIGNAL LOCK :STD_LOGIC;BEGINADDA<='1'LOCK1<=LOCK;PRO:PROCESS(current_state,EOC) BEGINCASE c

4、urrent_state ISWHEN st0=> ALE<='0'START<='0'OE<='0'LOCK<='0' next_state<=st1;WHEN st1=> ALE<='1'START<='0'OE<='0'LOCK<='0' next_state<=st2;WHEN st2=> ALE<='0'START<='1'OE<=

5、'0'LOCK<='0' next_state<=st3;WHEN st3=> ALE<='0'START<='0'OE<='0'LOCK<='0'IF(EOC='1')THEN next_state<=st3;ELSE next_state<=st4;END IF;WHEN st4=>ALE<='0'START<='0'OE<='0'LOCK<=

6、9;0'IF(EOC='0')THEN next_state<=st4;ELSE next_state <=st5;END IF;WHEN st5=>ALE<='0'START<='0'OE<='1'LOCK<='0' next_state<=st6;WHEN st6=>ALE<='0'START<='0'OE<='1'LOCK<='1' next_state<

7、=st0;WHEN OTHERS=>ALE<='0'START<='0'OE<='0'LOCK<='0' next_state<=st0;END CASE;END PROCESS PRO;PROCESS(CLK) BEGINIF(CLK'EVENT AND CLK='1') THEN current_state<=next_state;END IF;END PROCESS;PROCESS(LOCK)BEGINIF LOCK='1' AND LOCK'EVENT THEN REGL<=D;END IF;END PROCESS;Q<=REGL;END behav;仿真圖：主要控制信號說明：Start為轉(zhuǎn)換啟動信號，高電平有效；ale為通道選擇地址信號的鎖存信號。當(dāng)啟動轉(zhuǎn)換后，程序開始執(zhí)行，查詢狀態(tài)，狀態(tài)為0.1.2時等待，狀態(tài)3時，查詢EDC信號的狀態(tài)，判斷是否轉(zhuǎn)換結(jié)束，當(dāng)EDC下降沿