序言
這個是我在做FPGA界的HelloWorld——數字鍾設計時隨手寫下的，再現了數字鍾設計的過程
目標分析
- 時鍾具有時分秒的顯示，需6個數碼管。為了減小功耗采用掃描法顯示
- 按鍵設置時間，需要對按鍵進行消抖
- 時分秒即為2個60進制計數器，一個24進制計數器。
模塊設計
綜上所述，我采用模塊化設計方法進行設計，繪制框圖如下。
- 時鍾分頻產生各個模塊所需頻率時鍾。
- 按鍵處理模塊對按鍵信號進行消抖、變長脈沖為短脈沖等處理。
- 時間控制模塊產生時間信號或對時間進行設置。
- 數碼管驅動模塊負責對時間信號BCD碼譯碼為數碼管的段碼並且掃描輸出到數碼管。
下面對各個模塊分別詳細敘述
時鍾分頻模塊
我打算把時鍾分頻模塊做成“數控N分頻器”，通過給分頻器傳入數值N來對時鍾信號進行N分頻。得到的信號頻率為原時鍾信號的頻率/N,占空比為1/N。
稍微考慮下其他模塊所需時鍾：按鍵處理模塊100Hz ，時間控制模塊1Hz，數碼管驅動50Hz。而輸入時鍾為33.8688MHz。
我不想傳入的N數值過大，我打算先對時鍾進行兩次：第一次調用時鍾分頻模塊得到1Mhz，第二次得到1Khz。這樣N的位數為10可以滿足需求。
代碼如下
library IEEE;
use IEEE.STD_LOGIC_1164.all;
use IEEE.STD_LOGIC_UNSIGNED.all;
entity ClkDiv is
port(
clk_i:IN STD_LOGIC;
N_i: IN STD_LOGIC_VECTOR(9 DOWNTO 0);
clk_o:OUT STD_LOGIC);
end ClkDiv;
architecture behavior of ClkDiv is
signal count:STD_LOGIC_VECTOR(9 DOWNTO 0):="0000000001";
signal clk_temp:STD_LOGIC:='0';
begin
process(clk_i)
begin
if(clk_i'EVENT and clk_i='1')then
if (count=N_i)then
count<="0000000001";
clk_temp<='1';
else
count<=count+1;
clk_temp<='0';
end if;
end if;
end process;
clk_o<=clk_temp;
end behavior;
仿真結果如下：
2分頻：輸出信號為f/2Hz，占空比1：2
3分頻：輸出信號為f/3Hz，占空比1：3
按鍵處理模塊
去抖動根據以往的經驗，按鍵按下彈起電平會有一小段毛刺，可能會引起電路誤操作，所以要對按鍵進行消抖處理使變為干凈的矩形信號。
抖動時間一般為10ms，若采樣時間為10ms則噪聲最多采樣到一次。
對於兩級D觸發器，Q1和Q2之間有一個時間延遲效果。每一次時鍾上升沿就是對信號采樣一次，Q1保存的是最新一次的采樣，Q2保存的是上一次的采樣，Q1和Q2之間有一個時間延遲，時間為時鍾周期。
對於噪聲信號只能采樣到一次，Q1*Q2的值一定為0。
對於持續時間大於時鍾周期的信號可以采樣到兩次，Q1的值和Q2的值相同，Q1*Q2為信號電平。這就是去抖原理。
代碼如下
library IEEE;
use IEEE.STD_LOGIC_1164.all;
use IEEE.STD_LOGIC_UNSIGNED.all;
entity JitterElimination is
port(
key: IN STD_LOGIC;
clk_i:IN STD_LOGIC;
DLY_OUT:OUT STD_LOGIC);
end JitterElimination;
architecture rtl of JitterElimination is
signal D1,D2,S:STD_LOGIC;
begin
process(clk_i)
begin
if (clk_i'EVENT and clk_i='1')then
D1<=key;
D2<=D1;
end if;
end process;
S<=D1 and D2;
DLY_OUT<=S;
end rtl;
仿真結果如下
可以看到，按鍵的抖動被消除了，但是可以看到按鍵按下電平持續時間跨過幾個時鍾周期。如果有必要可以使用微分電路把矩形波轉換為窄脈沖波，這里不需要。
數碼管驅動模塊
時分秒顯示需要2+2+2=6個數碼管，每個數碼管的顯示需要8根引腳。使用掃描方式顯示，只需要6+8=14根引腳，功耗比較低。
輸入：時間信號BCD碼有4*6=24位，用於控制掃描頻率的時鍾信號是1個輸入信號
輸出：位選信號6位，段碼8位
library IEEE;
use IEEE.STD_LOGIC_1164.all;
entity LEDScan is
port(
CurTime_i: IN STD_LOGIC_VECTOR(23 DOWNTO 0);
clk_i:IN STD_LOGIC;
Position_o:OUT STD_LOGIC_VECTOR(5 DOWNTO 0);
Section_o: OUT STD_LOGIC_VECTOR(7 DOWNTO 0));
function convert(BCD:STD_LOGIC_VECTOR(3 DOWNTO 0)) return STD_LOGIC_VECTOR is
variable Section: STD_LOGIC_VECTOR(7 DOWNTO 0);
begin
Case BCD is
when "0000" =>Section:="00111111"; --段碼表————————————---------------------------------------------
when "0001" =>Section:="00000110"; --0x3f,0x06,0x5b,0x4f,0x66,
when "0010" =>Section:="01011011"; --0x6d,0x7d,0x07,0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71
when "0011" =>Section:="01001111";
when "0100" =>Section:="01100110";
when "0101" =>Section:="01101101";
when "0110" =>Section:="01111101";
when "0111" =>Section:="00000111";
when "1000" =>Section:="01111111";
when "1001" =>Section:="01101111";
when OTHERS =>Section:="01100110";--01110001
-- when "0000" =>Section:="11000000"; --段碼表{0x88,0x83,0xc6,0xa1,0x86,0x8e}----------------
-- when "0001" =>Section:="11111001"; --0xc0,0xf9,0xa4,0xb0,0x99,
-- when "0010" =>Section:="10100100"; --0x92,0x82,0xf8, 0x80,0x90,
-- when "0011" =>Section:="10110000";
-- when "0100" =>Section:="10011001";
--
-- when "0101" =>Section:="10010010";
-- when "0110" =>Section:="10000010";
-- when "0111" =>Section:="11111000";
-- when "1000" =>Section:="10000000";
-- when "1001" =>Section:="10010000";
-- when OTHERS =>Section:="10001110";
end case;
return Section;
end convert;
end LEDScan;
architecture behaviour of LEDScan is
signal CurTimeTemp:STD_LOGIC_VECTOR(23 DOWNTO 0):="000000000000000000000000";
signal SectionTemp,Section0,Section1,Section2,Section3,Section4,Section5: STD_LOGIC_VECTOR(7 DOWNTO 0):="00111111";--此處應為0的段碼，數碼管共陰數碼管-----------------------------------------------------------------------
signal Position :integer :=5;
begin
process(clk_i)
begin
if (clk_i'EVENT and clk_i='1') then
CurTimeTemp<=CurTime_i;
Section0<=convert(CurTimeTemp(3 DOWNTO 0));
Section1<=convert(CurTimeTemp(7 DOWNTO 4));
Section2<=convert(CurTimeTemp(11 DOWNTO 8));
Section3<=convert(CurTimeTemp(15 DOWNTO 12));
Section4<=convert(CurTimeTemp(19 DOWNTO 16));
Section5<=convert(CurTimeTemp(23 DOWNTO 20));
if (Position=5)then
Position<=0;
else
Position<=Position+1;
end if;
case Position is
when 0 =>Section_o<=Section0;Position_o<="000001";
when 1 =>Section_o<=Section1;Position_o<="000010";
when 2 =>Section_o<='1'&Section2(6 downto 0);Position_o<="000100"; --添加小數點
when 3 =>Section_o<=Section3;Position_o<="001000";
when 4 =>Section_o<='1'&Section4(6 downto 0);Position_o<="010000";
when 5 =>Section_o<=Section5;Position_o<="100000";
when OTHERS=>NULL;
end case;
end if;
end process;
end behaviour;
仿真結果如下圖所示
我們可以看到在當前時間為23:59:59的情況下Section5里面放的是2的段碼，Section4里面放的是3的段碼，Section3里面放的是5的段碼
在時鍾的作用下，Position_o依次選中個位，Section_o輸出的是選中位置的段碼。
時間控制模塊
我想用兩個按鍵分別設置分鍾，時鍾數值。分鍾增1的條件是按鍵按下或者秒計數器進位，時鍾增1的條件是按鍵2按下或者分鍾計數器進位。這樣可以在不破壞正常運行狀態的情況下，用按鍵對分、時進行加1操作(設置)，滿足了功能又沒有增加設計的復雜度。
最后將計數器的值翻譯為BCD碼，連接到一起形成24位BCD碼。
輸入：按鍵1和按鍵2、1Hz時間脈沖
輸出：24位BCD碼
N進制計數器
library IEEE;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
use ieee.numeric_std.all;
entity Counter is
port(
CountClk:in STD_LOGIC;
N: in STD_LOGIC_VECTOR(4 downto 0);
count:out STD_LOGIC_VECTOR(4 downto 0);
Cout:out STD_LOGIC);
end Counter;
architecture behav of Counter is
signal count_temp: STD_LOGIC_VECTOR(4 downto 0):="00000";
signal CoutTemp:STD_LOGIC:='0';
begin
process(CountClk)
begin
if (CountClk'EVENT and CountClk='1')then
count_temp<=count_temp+1;
CoutTemp<='0';
if (count_temp>=N)then
count_temp<="00000";
CoutTemp<='1';
end if;
end if;
end process;
Cout<=CoutTemp;
count<=count_temp;
end behav;
控制模塊
library IEEE;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
use ieee.numeric_std.all;
entity Contrl is
port(
MinKey_i:IN STD_LOGIC;
HourKey_i:IN STD_LOGIC;
clk_i:IN STD_LOGIC;
CurrentTimeBCD_o: OUT STD_LOGIC_VECTOR(23 downto 0));
end Contrl;
architecture behavior of Contrl is
signal h: integer range 0 to 23 := 0; -- 秒鍾個位
signal m: integer range 0 to 59 := 0; -- 秒鍾個位
signal s: integer range 0 to 59 := 0; -- 秒鍾個位
signal s1: integer range 0 to 9 := 0; -- 秒鍾個位
signal s2: integer range 0 to 5 := 0; -- 秒鍾百位
signal m1: integer range 0 to 9 := 0; -- 分鍾個位
signal m2: integer range 0 to 5 := 0; -- 分鍾百位
signal h1: integer range 0 to 9 := 0; -- 時鍾個位
signal h2: integer range 0 to 2 := 0; -- 時鍾百位
signal CurrentTimeBCD : STD_LOGIC_VECTOR(23 downto 0):="000000000000000000000000";
constant N9:STD_LOGIC_VECTOR(4 downto 0):="01001";
constant N5:STD_LOGIC_VECTOR(4 downto 0):="00101";
constant N1:STD_LOGIC_VECTOR(4 downto 0):="00001";
constant N23:STD_LOGIC_VECTOR(4 downto 0):="10111";
signal CountS1:STD_LOGIC_VECTOR(4 downto 0):="00000";
signal CountS2:STD_LOGIC_VECTOR(4 downto 0):="00000";
signal CountH:STD_LOGIC_VECTOR(4 downto 0):="00000";
signal CountM1:STD_LOGIC_VECTOR(4 downto 0):="00000";
signal CountM2:STD_LOGIC_VECTOR(4 downto 0):="00000";
signal CountH1:STD_LOGIC_VECTOR(4 downto 0):="00000";
signal CountH2:STD_LOGIC_VECTOR(4 downto 0):="00000";
signal KeyMTemp:STD_LOGIC:='1';
signal KeyHTemp:STD_LOGIC:='1';
signal CoutS1:STD_LOGIC:='0';
signal CoutS2:STD_LOGIC:='0';
signal CoutM1:STD_LOGIC:='0';
signal CoutM2:STD_LOGIC:='0';
signal CoutH:STD_LOGIC:='0';
signal CoutH1:STD_LOGIC:='0';
signal CoutH2:STD_LOGIC:='0';
component Counter is
port(
CountClk:in STD_LOGIC;
N: in STD_LOGIC_VECTOR(4 downto 0);
count:out STD_LOGIC_VECTOR(4 downto 0);
Cout:out STD_LOGIC);
end component;
begin
KeyMTemp<=CoutS2 xor (not MinKey_i);
KeyHTemp<=CoutM2 xor (not HourKey_i);
S1_Map: Counter port map(
CountClk=> clk_i,
N=>N9,
count=>CountS1,
cout=>CoutS1);
S2_Map: Counter port map(
CountClk=> CoutS1,
N=>N5,
count=>CountS2,
cout=>CoutS2);
M1_Map: Counter port map(
CountClk=>KeyMTemp ,
N=>N9,
count=>CountM1,
cout=>CoutM1);
M2_Map: Counter port map(
CountClk=> CoutM1,
N=>N5,
count=>CountM2,
cout=>CoutM2);
H1_Map: Counter port map(
CountClk=> KeyHTemp,
N=>N23,
count=>CountH,
cout=>CoutH);
process(CountH)
begin
case CountH is
when "00000" =>CountH2<="00000";CountH1<="00000";
when "00001" =>CountH2<="00000";CountH1<="00001";
when "00010" =>CountH2<="00000";CountH1<="00010";
when "00011" =>CountH2<="00000";CountH1<="00011";
when "00100"=>CountH2<="00000";CountH1<="00100";
when "00101" =>CountH2<="00000";CountH1<="00101";
when "00110" =>CountH2<="00000";CountH1<="00110";
when "00111" =>CountH2<="00000";CountH1<="00111";
when "01000" =>CountH2<="00000";CountH1<="01000";
when "01001" =>CountH2<="00000";CountH1<="01001";
when "01010"=>CountH2<="00001";CountH1<="00000";
when "01011" =>CountH2<="00001";CountH1<="00001";
when "01100" =>CountH2<="00001";CountH1<="00010";
when "01101" =>CountH2<="00001";CountH1<="00011";
when "01110" =>CountH2<="00001";CountH1<="00100";
when "01111" =>CountH2<="00001";CountH1<="00101";
when "10000" =>CountH2<="00001";CountH1<="00110";
when "10001" =>CountH2<="00001";CountH1<="00111";
when "10010" =>CountH2<="00001";CountH1<="01000";
when "10011" =>CountH2<="00001";CountH1<="01001";
when "10100" =>CountH2<="00010";CountH1<="00000";
when "10101" =>CountH2<="00010";CountH1<="00001";
when "10110" =>CountH2<="00010";CountH1<="00010";
when "10111" =>CountH2<="00010";CountH1<="00011";
when OTHERS=>NULL;
end case;
-- process(HourKey_i)
-- begin
-- if (HourKey_i'EVENT and HourKey_i='1') then
-- if h<23 then
-- h<=h+1;
-- else
-- h<=0;
-- end if;
-- end if;
-- end process;
--
-- process(MinKey_i)
-- begin
-- if (MinKey_i'EVENT and MinKey_i='1') then
-- if m<59 then
-- m<=m+1;
-- else
-- m<=0;
-- end if;
-- end if;
-- end process;
-- if s1<9 then
-- s1<=s1+1;
-- else
-- s1<=0;
-- if s2<5 then
-- s2<=s2+1;
-- else
-- s2<=0;
-- if m1<9 then
-- m1<=m1+1;
-- else
-- m1<=0;
-- if m2<5 then
-- m2<=m2+1;
-- else
-- m2<=0;
-- if h2<2 then
-- if h1<9 then
-- h1<=h1+1;
-- else
-- h1<=0;
-- h2<=h2+1;---可以斷定這里加一
-- end if;
-- elsif h2>1 then
-- if h1<3 then
-- h1<=h1+1;
-- else
-- h1<=0;
-- h2<=0;
-- end if;
-- end if;
-- end if;
-- end if;
-- end if;
-- end if;
-- end if ;
--
-- if (MinKey_i'EVENT and MinKey_i='1') then ------可能要根據按鍵高電平有效還是低電平有效修改 假設按下接到地
-- if m1<=9 then
-- m1<=m1+1;
-- else
-- m1<=0;
-- if m2<=5 then
-- m2<=m2+1;
-- else
-- m2<=0;
-- end if;
-- end if;
-- end if;
-- if (HourKey_i'EVENT and HourKey_i='1') then ------可能要根據按鍵高電平有效還是低電平有效修改
-- if h2<2 then
-- if h1<9 then
-- h1<=h1+1;
-- else
-- h1<=0;
-- h2<=h2+1;---可以斷定這里加一
-- end if;
-- elsif h2>1 then
-- if h1<3 then
-- h1<=h1+1;
-- else
-- h1<=0;
-- h2<=0;
-- end if;
-- end if;
-- end if;
--
--
--
--
-- IF(clk_i'EVENT and clk_i='1')then
-- if (HourKey_i='0') then
-- if h<23 then
-- h<=h+1;
-- else
-- h<=0;
-- end if;
-- end if;
--
-- if ( MinKey_i='0') then
-- if m<59 then
-- m<=m+1;
-- else
-- m<=0;
-- end if;
-- end if;
--
-- if s<59 then
-- s<=s+1;
-- else
-- s<=0;
-- if m<59 then
-- m<=m+1;
-- else
-- m<=0;
-- if h<23 then
-- h<=h+1;
-- else
-- h<=0;
-- end if;
-- end if;
-- end if;
--
--
--
-- end if;
--
--
--
--
--
--
-- h1<=h mod 10;
-- h2<=(h - h1)/10;
--
-- m1<=m mod 10;
-- m2<=(m - m1)/10;
--
-- s1<=s mod 10;
-- s2<=(s - s1)/10;
--
--
--
s1<=CONV_INTEGER(CountS1);
s2<=CONV_INTEGER(CountS2);
m1<=CONV_INTEGER(CountM1);
m2<=CONV_INTEGER(CountM2);
h1<=CONV_INTEGER(CountH1);
h2<=CONV_INTEGER(CountH2);
CurrentTimeBCD(3 downto 0) <= std_logic_vector(to_unsigned(s1, 4));
CurrentTimeBCD(7 downto 4) <= std_logic_vector(to_unsigned(s2, 4));
CurrentTimeBCD(11 downto 8) <= std_logic_vector(to_unsigned(m1, 4));
CurrentTimeBCD(15 downto 12) <= std_logic_vector(to_unsigned(m2, 4));
CurrentTimeBCD(19 downto 16) <= std_logic_vector(to_unsigned(h1, 4));
CurrentTimeBCD(23 downto 20) <= std_logic_vector(to_unsigned(h2, 4));
end process;
CurrentTimeBCD_o<=CurrentTimeBCD;
end behavior;
仿真結果如下
小時
分鍾
秒鍾
下圖中輸出CurrentTimeBCD_o旁邊的數值105238表示帶有時間信息的BCD碼表示的時間10點52分38秒
頂層模塊
頂層模塊就是把上面各個模塊根據下圖用線連接起來。下圖為簡潔只畫了一個按鍵
稍微分析端口：
輸入：按鍵1、按鍵2、時鍾輸入
輸出：6位的位選信號、8位的段碼信號
代碼如下
library IEEE;
use IEEE.STD_LOGIC_1164.all;
entity DigitalClock is
port(
DigitalClockClk_i:IN STD_LOGIC;
DigitalClockKeyM_i:IN STD_LOGIC;
DigitalClockKeyH_i:IN STD_LOGIC;
DigitalClockPosition_o:OUT STD_LOGIC_VECTOR(5 DOWNTO 0);
DigitalClockSection_o: OUT STD_LOGIC_VECTOR(7 DOWNTO 0));
end DigitalClock;
architecture rtl of DigitalClock is
component ClkDiv is
port(
clk_i:IN STD_LOGIC;
N_i: IN STD_LOGIC_VECTOR(9 DOWNTO 0);
clk_o:OUT STD_LOGIC);
end component;
component JitterElimination is
port(
key: IN STD_LOGIC;
clk_i:IN STD_LOGIC;
DLY_OUT:OUT STD_LOGIC);
end component;
component LEDScan is
port(
CurTime_i: IN STD_LOGIC_VECTOR(23 DOWNTO 0);
clk_i:IN STD_LOGIC;
Position_o:OUT STD_LOGIC_VECTOR(5 DOWNTO 0);
Section_o: OUT STD_LOGIC_VECTOR(7 DOWNTO 0));
end component;
component Contrl is
port(
MinKey_i:IN STD_LOGIC;
HourKey_i:IN STD_LOGIC;
clk_i:IN STD_LOGIC;
CurrentTimeBCD_o: OUT STD_LOGIC_VECTOR(23 downto 0));
end component;
signal N1: STD_LOGIC_VECTOR(9 DOWNTO 0):="0000100010";
signal Clk1M: STD_LOGIC:='0';
signal N2: STD_LOGIC_VECTOR(9 DOWNTO 0):="1111101000";
signal Clk1k: STD_LOGIC:='0';
signal N3: STD_LOGIC_VECTOR(9 DOWNTO 0):="0000001010";
signal Clk100Hz: STD_LOGIC:='0';
signal N4: STD_LOGIC_VECTOR(9 DOWNTO 0):="0000000010";
signal Clk50Hz: STD_LOGIC:='0';
signal N5: STD_LOGIC_VECTOR(9 DOWNTO 0):="0000110010";
signal Clk1Hz: STD_LOGIC:='0';
signal K1:STD_LOGIC:='1';--未按下
signal K2:STD_LOGIC:='1';--未按下
signal BCD:STD_LOGIC_VECTOR(23 downto 0):="000000000000000000000000";
begin
Clock_Map: ClkDiv port map(
clk_i=>DigitalClockClk_i,
N_i=>N1,
clk_o=>Clk1M);
Clock_Map2: ClkDiv port map(
clk_i=>Clk1M,
N_i=>N2,
clk_o=>Clk1k);
Clock_Map3: ClkDiv port map(
clk_i=>Clk1k,
N_i=>N3,
clk_o=>Clk100Hz);
Clock_Map4: ClkDiv port map(
clk_i=>Clk100Hz,
N_i=>N4,
clk_o=>Clk50Hz);
Clock_Map5: ClkDiv port map(
clk_i=>Clk50Hz,
N_i=>N5,
clk_o=>Clk1Hz);
KeyMin_Map:JitterElimination port map(
key=>DigitalClockKeyM_i,
clk_i=>Clk100Hz,
DLY_OUT=>K1);
KeyHour_Map:JitterElimination port map(
key=>DigitalClockKeyH_i,
clk_i=>Clk100Hz,
DLY_OUT=>K2);
Contrl_Map: Contrl port map(
MinKey_i=>K1,
HourKey_i=>K2,
clk_i=>Clk1Hz,
CurrentTimeBCD_o=>BCD);
LEDScan_Map: LEDScan port map(
CurTime_i=>BCD,
clk_i=>Clk1k,
Position_o=>DigitalClockPosition_o,
Section_o=>DigitalClockSection_o);
end rtl;
由於33.8688Mhz太大，軟件仿真時間會比較慢，所以我沒有把軟件仿真圖放出來。等過些時候到FPGA板子上驗證
實驗結果：符合設計預期結果，時分秒顯示、按鍵都正常。
誤差分析
由於1Mhz的時鍾是由33.8688Mhz經過34分頻生成的，所以每秒會有0.1078s的誤差，也就是說1s過后此數字鍾覺得時間過了1.1078s。分頻方面我欠考慮了，如果想要提高精度要在分頻方面思考。
生成原理圖
尾聲
新司機上路，各位系好安全帶