bfl_encode.vhd

将宽度为width位的并行输入数据按BiΦ-L码(曼彻斯特码)方式进行编码后串行输出

-- *******************************************************************************************
-- File name    : BFL_Encode.vhd
-- Created On   : 2008-03-21 16:25
-- Designed by  : He Minghui
-- Function     : 将宽度为width位的输入数据按BiΦ-L方式(曼彻斯特码)进行编码后输出，输出数据的宽度为(2*width)
-- *******************************************************************************************

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

ENTITY BFL_Encode is
	GENERIC(width: INTEGER := 16);
	PORT
	(
		Data     : IN STD_LOGIC_VECTOR(width-1 DOWNTO 0);
		nReset   : IN STD_LOGIC;
		WriteData: IN STD_LOGIC;
		Lsb_first: IN STD_LOGIC;
		BFL_Data : OUT STD_LOGIC_VECTOR(width*2-1 DOWNTO 0)
		);
END BFL_Encode;

ARCHITECTURE Behave OF BFL_Encode IS
BEGIN
-- *******************************************************************************************
	PROCESS(WriteData,nReset)
		VARIABLE Data_Temp: STD_LOGIC_VECTOR(width-1 downto 0);
		VARIABLE BFL_Temp : STD_LOGIC_VECTOR(width*2-1 downto 0);
		VARIABLE HighLevel: STD_LOGIC;
	BEGIN
		IF nReset = '0' THEN
			BFL_Temp := (OTHERS => '0');
		--	BFL_Data <= (OTHERS => '0');
		ELSIF rising_edge(WriteData) THEN
			Data_Temp := Data;

			FOR i IN 0 TO (width-1) LOOP
				IF(Lsb_first = '1')THEN  -- 先发送低位，后发送高位
					IF  Data_Temp(i) = '1' THEN
						BFL_Temp(2*i+1) := '0';
						BFL_Temp(2*i)   := '1';
					ELSE
						BFL_Temp(2*i+1) := '1';
						BFL_Temp(2*i)   := '0';
					END IF;
				ELSE  -- 先发送高位，后发送低位
					IF  Data_Temp(i) = '1' THEN
						BFL_Temp(2*i+1) := '1';
						BFL_Temp(2*i)   := '0';
					ELSE
						BFL_Temp(2*i+1) := '0';
						BFL_Temp(2*i)   := '1';
					END IF;
				END IF;
			END LOOP;
			BFL_Data <= BFL_Temp;
		END IF;
	END PROCESS;
-- *******************************************************************************************
END Behave;

-- 高位先发：指的是转化后的串行数据由高至低的顺序发送
-- 低位先发：指的是转化后的串行数据由低至高的顺序发送