fifo.vhd

VHDL的例子

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_ARITH.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;

ENTITY Tx_Sla IS
		PORT(			
			TxSoc 					: IN  STD_LOGIC;
			Clock			   		: IN  STD_LOGIC; --CLK FROM 8260
			Txdata					: IN  STD_LOGIC_VECTOR(15 DOWNTO 0);
			TxAddr               		: IN  STD_LOGIC_VECTOR(4 DOWNTO 0);
			TxClav  				   	: OUT STD_LOGIC;
			TxEnb                		: IN STD_LOGIC;
         		In_data					: OUT STD_LOGIC_VECTOR(15 DOWNTO 0);
			Write_en				   	: OUT STD_LOGIC;
			ResetB					: IN  STD_LOGIC;
			Wrclav					: IN  STD_LOGIC
			);
ENDTx_Sla;

ARCHITECTURE RTL OF Tx_Sla IS
			
			SIGNAL TxEnb_tmp			: STD_LOGIC;
			SIGNAL Byte_Count			: STD_LOGIC_VECTOR(4 DOWNTO 0);
		
			TYPE   Poll_State_TYPE 		IS 	(S0,S1,S2);
			SIGNAL Poll_state			: Poll_State_TYPE;
			SIGNAL Data				: STD_LOGIC_VECTOR(15 DOWNTO 0);
		
BEGIN

	Justify:	--接收轮询地址并验证，如物理地址为0，则发送CLAV
	PROCESS(Clock,ResetB)
	BEGIN
		IF (ResetB = '0') Then      --复位逻辑，将状态清零
			Poll_state<= S0;
			Byte_Count<="00000"	;	
         		Write_en<='0';	
		ELSIF (Clock'EVENT AND Clock = '1') THEN
			CASE  Poll_state IS
WHEN S0 =>   --	如果FIFO内有空间并且轮询地址为0，TXENB为高电平，--送出TXCLAV
				IF(TxAddr="00000"and Wrclav='1' )  THEN
					IF(TxEnb='1')     THEN
                  			TxClav<='1';
						Poll_state<= S1;
                  		ELSE 
                  			TxClav<='1';
						Poll_state<= S0;
                  END IF;
				ELSIF(TxAddr="11111") THEN
					   	TxClav<='Z';		
                  			Poll_state<= S0;
				ELSE
                  			TxClav<='0';
                  			Poll_state<= S0;
				END IF;		
			WHEN S1 =>   --如果主设备送出TXSOC则准备接收数据
		          IF(TxAddr="00000"and Wrclav='1')  THEN
                     		TxClav<='1';
                   ELSIF(TxAddr="11111") THEN
                           	TxClav<='Z';  
                   ELSE
                            TxClav<='0';
                  	END IF;				
				IF (TxSoc='1' )   THEN
                  			In_data<=  Txdata;
                  			Byte_Count<=Byte_Count+'1';
                  			Write_en<='1';	
				      	Poll_state<= S2;
                 	ELSE
					   	Poll_state<= S0;
				END IF;
				WHEN S2 =>     如果接收数据达到帧里的字节数，则停止接收
                   IF(TxAddr="00000"and Wrclav='1')  then 
                     TxClav<='1';
                   ELSIF(TxAddr="11111") THEN
                           	TxClav<='Z'	;  
                   ELSE
                            TxClav<='0'	;
                   END IF;
               	IF(Byte_Count="11011") THEN
               			Write_en<='0';
               			Byte_Count<="00000";	
                  			Poll_state<= S0;
               	ELSE
               			In_data<=  Txdata;
    				   		Write_en<='1';	
                  			Byte_Count<=Byte_Count+'1';
                  			Poll_state<= S2;                  
				END if;						
				END  CASE;
			END IF;
	END PROCESS Justify;
END RTL;