1. LED流水灯的FPGA代码
一个使用状态机思想来实现LED流水灯的FPGA代码
这个例子采用VHDL编写
VHDL代码示例：
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;entity led_flowing isPort ( clk : in std_logic;reset : in std_logic;led : out std_logic_vector(7 downto 0));
end led_flowing;architecture Behavioral of led_flowing istype state_type is (s0, s1, s2, s3, s4, s5, s6, s7);signal current_state, next_state : state_type;signal count : integer := 0;beginprocess(clk, reset)beginif reset = '1' thencurrent_state <= s0;elsif rising_edge(clk) thencurrent_state <= next_state;end if;end process;process(current_state)begincase current_state iswhen s0 =>led <= "00000001"; -- 灯1亮next_state <= s1;when s1 =>led <= "00000010"; -- 灯2亮next_state <= s2;when s2 =>led <= "00000100"; -- 灯3亮next_state <= s3;when s3 =>led <= "00001000"; -- 灯4亮next_state <= s4;when s4 =>led <= "00010000"; -- 灯5亮next_state <= s5;when s5 =>led <= "00100000"; -- 灯6亮next_state <= s6;when s6 =>led <= "01000000"; -- 灯7亮next_state <= s7;when s7 =>led <= "10000000"; -- 灯8亮next_state <= s0;when others =>led <= "00000000"; -- 关闭所有灯next_state <= s0;end case;end process;end Behavioral;
仿真测试代码：
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;entity tb_led_flowing is
end tb_led_flowing;architecture Behavioral of tb_led_flowing issignal clk : std_logic := '0';signal reset : std_logic := '0';signal led : std_logic_vector(7 downto 0);constant CLK_PERIOD : time := 10 ns;beginuut: entity work.led_flowingport map (clk => clk,reset => reset,led => led);-- Clock generationclk_process :processbeginwhile True loopclk <= '0';wait for CLK_PERIOD/2;clk <= '1';wait for CLK_PERIOD/2;end loop;end process;-- Stimulus processstim_proc: processbeginreset <= '1';wait for 20 ns;reset <= '0';wait for 300 ns; -- 放置足够的时间进行观察assert false report "End of simulation" severity note;wait;end process;end Behavioral;
流水灯演示：
2. CPLD和FPGA芯片的主要技术区别
CPLD（复杂可编程逻辑器件）与FPGA（现场可编程门阵列）的主要区别：
1、结构与规模：
CPLD：通常具有较小的逻辑单元和较低的延迟，适合简单的组合逻辑和小规模状态机。FPGA：具有较大的逻辑块（逻辑单元），可以支持更复杂的设计和更高的并行处理能力。
2、应用场合：
CPLD：适合用于控制逻辑、状态机、小型接口或数据处理，通常用于低功耗、高速的应用。244FPGA：适用于需要处理大量并行信号和复杂算法的应用，如图像处理、数据加速等。
