在下面横线上填上合适的语句，完成一个10线－4线优先编码器的设计。 LIBRARY IEEE ; USE IEEE.STD_LOGIC_1164.ALL; ENTITY CODER IS PORT ( DIN : IN STD_LOGIC_VECTOR(9 DOWNTO 0); OUTPUT : OUT STD_LOGIC_VECTOR(3 DOWNTO 0) ); END CODER; ARCHITECTURE BEHAV OF CODER IS SIGNAL SIN : STD_LOGIC_VECTOR(3 DOWNTO 0); BEGIN PROCESS ( 1 ) BEGIN IF (DIN(9)='0') THEN SIN <= "1001" ; 2 (DIN(8)=’0’) THEN SIN <= "1000" ; ELSIF (DIN(7)='0') THEN SIN <= "0111" ; ELSIF (DIN(6)='0') THEN SIN <= "0110" ; ELSIF (DIN(5)='0') THEN SIN <= "0101" ; ELSIF (DIN(4)='0') THEN SIN <= "0100" ; ELSIF (DIN(3)='0') THEN SIN <= "0011" ; ELSIF (DIN(2)='0') THEN SIN <= "0010" ; ELSIF (DIN(1)='0') THEN SIN <= "0001" ; ELSE SIN <= “0000”； 3 ； END PROCESS ； OUTPUT <= SIN ； END BEHAV;

完整代码如下：

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;

ENTITY PRIORITY_ENCODER IS
    PORT (
        DIN : IN STD_LOGIC_VECTOR(9 DOWNTO 0);
        OUTPUT : OUT STD_LOGIC_VECTOR(3 DOWNTO 0)
    );
END PRIORITY_ENCODER;

ARCHITECTURE BEHAV OF PRIORITY_ENCODER IS
    SIGNAL SIN : STD_LOGIC_VECTOR(3 DOWNTO 0);
    BEGIN
        PROCESS (1)
        BEGIN
            IF (DIN(9)='0') THEN
                SIN <= "1001";
            ELSIF (DIN(8)='0') THEN
                SIN <= "1000";
            ELSIF (DIN(7)='0') THEN
                SIN <= "0111";
            ELSIF (DIN(6)='0') THEN
                SIN <= "0110";
            ELSIF (DIN(5)='0') THEN
                SIN <= "0101";
            ELSIF (DIN(4)='0') THEN
                SIN <= "0100";
            ELSIF (DIN(3)='0') THEN
                SIN <= "0011";
            ELSIF (DIN(2)='0') THEN
                SIN <= "0010";
            ELSIF (DIN(1)='0') THEN
                SIN <= "0001";
            ELSE
                SIN <= "0000";
            END IF;
        END PROCESS;
        
        -- 4-to-2 priority encoder
        PROCESS (SIN)
        BEGIN
            CASE SIN IS
                WHEN "1000" =>
                    OUTPUT <= "0000";
                WHEN "1001" =>
                    OUTPUT <= "0001";
                WHEN "1010" | "1100" =>
                    OUTPUT <= "0010";
                WHEN "1110" =>
                    OUTPUT <= "0011";
                WHEN "0111" =>
                    OUTPUT <= "0100";
                WHEN "0011" | "1011" =>
                    OUTPUT <= "0101";
                WHEN "0001" | "0101" | "0110" | "0110" | "1111" =>
                    OUTPUT <= "0110";
                WHEN "0010" | "0100" =>
                    OUTPUT <= "0111";
                WHEN "0000" =>
                    OUTPUT <= "1000";
                WHEN OTHERS =>
                    OUTPUT <= "XXXX";
            END CASE;
        END PROCESS;
    END BEHAV;

注释：这是一个10线-4线优先编码器，使用了两个PROCESS块。第一个PROCESS块将输入信号DIN编码成4位优先级编码SIN。第二个PROCESS块将SIN作为输入，根据编码规则输出4位优先级编码OUTPUT。如果输入信号中多个位为0，则输出的优先级编码为最高位为0的位的编码。如果所有位都是1，则输出的优先级编码为0000。如果输入信号中多个位为0，且这些位对应的编码相同，则输出编码最高的那个位的编码。如果输入信号中多个位为0，且这些位对应的编码不相同，则输出编码最高的那个位的编码。如果输入信号中有多个位为1，则输出编码最高的那个位的编码。如果输入信号中有多个位为0和多个位为1，则输出编码最高的那个位的编码。如果SIN中存在不合法的编码，则输出XXXX。