VHDL硬件描述语言实现数字钟

--VHDL上机的一个作业，程序太长实验报告册上写不下了。于是就在博客上留一份吧。
LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;

ENTITY CLOCK IS
PORT(CLK1S,SET,SWC,CLK1MS,RST:IN STD_LOGIC;
    S0,S1,M0,M1,H0,H1:OUT STD_LOGIC_VECTOR(3 DOWNTO 0);
    BEEP:OUT STD_LOGIC;
    PNS,PSS,PSM,PSH:OUT STD_LOGIC
);
END CLOCK;

ARCHITECTURE ONE OF CLOCK IS
SIGNAL CS,CM:STD_LOGIC;--,CM
SIGNAL CLKSI,CLKMI,CLKHI:STD_LOGIC;
SIGNAL NS,SS,SM,SH:STD_LOGIC;
BEGIN
PSS<=SS;
PSM<=SM;
PSH<=SH;
PNS<=NS;
PROCESS(SWC,RST)
VARIABLE STAT:STD_LOGIC_VECTOR(1 DOWNTO 0);
BEGIN
IF(RST='1')THEN
STAT:="00";
NS<='1';
SS<='0';
SM<='0';
SH<='0';
ELSIF(RISING_EDGE(SWC))THEN
STAT:=STAT+1;
CASE STAT IS
WHEN"00"=>
NS<='1';
SS<='0';
SM<='0';
SH<='0';
WHEN"01"=>
NS<='0';
SS<='1';
SM<='0';
SH<='0';
WHEN"10"=>
NS<='0';
SS<='0';
SM<='1';
SH<='0';
WHEN"11"=>
NS<='0';
SS<='0';
SM<='0';
SH<='1';
WHEN OTHERS=>
STAT:="00";
END CASE;
END IF;
END PROCESS;

CLKSI<=(CLK1S AND NS) OR (SS AND SET);
CLKMI<=CS OR (SM AND SET);
CLKHI<=CM OR (SH AND SET);

PROCESS(CLKSI,RST,SET,NS)
VARIABLE SS0,SS1:STD_LOGIC_VECTOR(3 DOWNTO 0);
BEGIN
IF(RST='1')THEN
SS0:="0000";
SS1:="0000";
CS<='0';
--CM<='0';
ELSIF(RISING_EDGE(CLKSI))THEN
SS0:=SS0+1;
IF(SS0="1010")THEN
SS0:="0000";
SS1:=SS1+1;
END IF;
IF(SS1="0110")THEN
SS1:="0000";
--SM0:=SM0+1;
CS<='1';
ELSE
CS<='0';
END IF;
END IF;
S0<=SS0;
S1<=SS1;
END PROCESS;

PROCESS(RST,CLKMI,SET)
VARIABLE SM0,SM1:STD_LOGIC_VECTOR(3 DOWNTO 0);
BEGIN
IF(RST='1')THEN
SM0:="0000";
SM1:="0000";
CM<='0';
ELSIF(RISING_EDGE(CLKMI))THEN
SM0:=SM0+1;
IF(SM0="1010")THEN
SM0:="0000";
SM1:=SM1+1;
END IF;
IF(SM1="0110")THEN
SM1:="0000";
CM<='1';
ELSE
CM<='0';
END IF;
END IF;
M0<=SM0;
M1<=SM1;
END PROCESS;

PROCESS(RST,CLKHI,SET)
VARIABLE SH0,SH1:STD_LOGIC_VECTOR(3 DOWNTO 0);
BEGIN
IF(RST='1')THEN
SH0:="0000";
SH1:="0000";
ELSIF(RISING_EDGE(CLKHI))THEN
SH0:=SH0+1;
IF(SH0="1010")THEN
SH0:="0000";
SH1:=SH1+1;
END IF;
IF(SH1="0010" AND SH0="0100")THEN
SH1:="0000";
SH0:="0000";
END IF;
END IF;
H0<=SH0;
H1<=SH1;
END PROCESS;

PROCESS(CM,CS)
BEGIN
IF(CM='1' AND CS='1')THEN
BEEP<=CLK1MS;
ELSE
BEEP<='0';
END IF;
END PROCESS;
END ONE;