VHDL设计的串口通信程序

               start_delaycnt <= ’0’;   
            END IF;
         ELSE
            IF ((NOT key_input=’1’) AND (cnt_delay = "00000000000000000000")) THEN
               start_delaycnt <= ’1’;   
            END IF;
         END IF;
      END IF;
   END PROCESS;

   PROCESS(clk,rst)
   BEGIN
      
      IF (NOT rst = ’1’) THEN
         key_entry1 <= ’0’;   
      ELSIF(clk’EVENT AND clk=’1’)THEN
         IF (key_entry2 = ’1’) THEN
            key_entry1 <= ’0’;   
         ELSE
            IF (cnt_delay = "11000011010100000000") THEN
               IF (NOT key_input = ’1’) THEN
                  key_entry1 <= ’1’;   
               END IF;
            END IF;
         END IF;
      END IF;
   END PROCESS;

   PROCESS(clk,rst)
   BEGIN
      
      IF (NOT rst = ’1’) THEN
         div_reg <= "0000000000000000";   
      ELSIF(clk’EVENT AND clk=’1’)THEN
         IF (div_reg = div_par - "0000000000000001") THEN
            div_reg <= "0000000000000000";   
         ELSE
            div_reg <= div_reg + "0000000000000001";   
         END IF;
      END IF;
   END PROCESS;

   PROCESS(clk,rst)  分频得到8倍波特率的时钟
   BEGIN
      
      IF (NOT rst = ’1’) THEN
         clkbaud8x <= ’0’;   
      ELSIF(clk’EVENT AND clk=’1’)THEN
         IF (div_reg = div_par - "0000000000000001") THEN
            clkbaud8x <= NOT clkbaud8x;   
         END IF;
      END IF;
   END PROCESS;

   PROCESS(clkbaud8x,rst)
   BEGIN
      IF (NOT rst = ’1’) THEN
         div8_rec_reg <= "000";   
      ELSE IF(clkbaud8x’EVENT AND clkbaud8x = ’1’) THEN
         IF (recstart = ’1’) THEN  接收开始标志
            div8_rec_reg <= div8_rec_reg + "001";接收开始后，时隙数在8倍波特率的时钟下加1循环   
         END IF;
    END IF;
      END IF;
   END PROCESS;

   PROCESS(clkbaud8x,rst)
   BEGIN
      IF (NOT rst = ’1’) THEN
         div8_tras_reg <= "000";   
      ELSE IF(clkbaud8x’EVENT AND clkbaud8x = ’1’) THEN
         IF (trasstart = ’1’) THEN
            div8_tras_reg <= div8_tras_reg + "001";发送开始后，时隙数在8倍波特率的时钟下加1循环   
         END IF;
    END IF;
      END IF;
   END PROCESS;

   PROCESS(div8_rec_reg)
   BEGIN
      IF (div8_rec_reg = "111") THEN
         clkbaud_rec <= ’1’; -在第7个时隙，接收  
      ELSE
         clkbaud_rec <= ’0’;   
      END IF;
   END PROCESS;

   PROCESS(div8_tras_reg)
   BEGIN
      IF (div8_tras_reg = "111") THEN
         clkbaud_tras <= ’1’;  在第7个时隙，发送使能信号有效，将数据发出 
      ELSE
         clkbaud_tras <= ’0’;   
      END IF;
   END PROCESS;

   PROCESS(clkbaud8x,rst)
   BEGIN
      IF (NOT rst = ’1’) THEN
         txd_reg <= ’1’;   
         trasstart <= ’0’;   
         txd_buf <= "00000000";   
         state_tras <= "0000";   
         send_state <= "000";   
         key_entry2 <= ’0’;   
      ELSE IF(clkbaud8x’EVENT AND clkbaud8x = ’1’) THEN
         IF (NOT key_entry2 = ’1’) THEN
            IF (key_entry1 = ’1’) THEN
               key_entry2 <= ’1’;   
               txd_buf <= "01110111";   "w"
            END IF;
         ELSE
            CASE state_tras IS
               WHEN "0000" =>  发送起始位
                        IF ((NOT trasstart=’1’) AND (send_state < "111") ) THEN
                           trasstart <= ’1’;   

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本文关键字：通信  程序  嵌入式系统-技术，单片机-工控设备 - 嵌入式系统-技术