poc.vhd

东南大学学生数字系统设计实验：用VHDL语言编写Printer与CPU互连的接口程序

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

ENTITY ENABLE IS
PORT(
	CLK:	IN STD_LOGIC;
	RESET:	IN STD_LOGIC;
	CS:		IN STD_LOGIC;
	ADDR:	IN STD_LOGIC_VECTOR(2 DOWNTO 0);
	DRIVE:	OUT STD_LOGIC	);
END ENABLE;

ARCHITECTURE BEHAVE OF ENABLE IS
BEGIN

PROCESS(CLK,RESET,ADDR,CS)
BEGIN 

IF CLK'EVENT AND CLK ='1' THEN
	IF RESET='0' AND CS='0' AND ADDR="101" THEN 
		DRIVE<='1';
	ELSE DRIVE<='0';
	END IF;
END IF;

END PROCESS;

END BEHAVE;


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

ENTITY CTRL IS
PORT (
        CLK:IN STD_LOGIC;
		EN:	IN STD_LOGIC;
		RW: IN STD_LOGIC;
		RDY:IN STD_LOGIC;
		TR:	OUT STD_LOGIC;
		DIN:IN STD_LOGIC_VECTOR(7 DOWNTO 0);
		PD:	OUT STD_LOGIC_VECTOR(7 DOWNTO 0)		);
END CTRL;

ARCHITECTURE BEHAVE OF CTRL IS
SIGNAL BR:STD_LOGIC_VECTOR(7 DOWNTO 0);
SIGNAL SR:STD_LOGIC_VECTOR(7 DOWNTO 0):="10000000";
SIGNAL COUNT:STD_LOGIC_VECTOR(2 DOWNTO 0):="000";

BEGIN


PROCESS(CLK,EN,RW,RDY,BR,SR)

BEGIN
	
IF EN='1' THEN
	IF CLK'EVENT AND CLK='1' THEN
		IF RW='1' THEN
			COUNT<=COUNT+1;
			PD<=BR;
			IF RDY='1' THEN
				TR<='1';
			ELSIF RDY='0' THEN
				TR<='0';
			END IF;
		ELSIF RW='0' THEN
			COUNT<=COUNT+1;
			PD<=X"00";
			IF SR(7)='1' AND SR(0)='0' THEN
				SR(7)<='0';
				BR<=DIN;
			END IF;
		END IF;
		IF COUNT="101" THEN
			SR(7)<='1';
			COUNT<="000";
		END IF;
	END IF;

ELSIF EN='0' THEN
	COUNT<="000";
	BR<=X"00";
	SR<=X"80";
END IF;

END PROCESS;

END BEHAVE;


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

ENTITY PRINTER IS
PORT (	CLK:	IN STD_LOGIC;
		RESET:	IN STD_LOGIC;
		TR:		IN STD_LOGIC;
		PD:		IN STD_LOGIC_VECTOR(7 DOWNTO 0);
		RDY:	OUT STD_LOGIC;
		PDOUT:	OUT STD_LOGIC_VECTOR(7 DOWNTO 0)	);
END PRINTER;

ARCHITECTURE BEHAVE OF PRINTER IS
SIGNAL COUNT:STD_LOGIC_VECTOR(2 DOWNTO 0);

BEGIN

PROCESS(CLK,RESET,COUNT,TR,PD)
BEGIN
IF RESET='0' THEN

	IF CLK'EVENT AND CLK='1' THEN
		COUNT<=COUNT+1;
		IF TR='1' THEN
			COUNT<="000";
			RDY<='0';
			PDOUT<=PD;
		ELSIF COUNT="101" THEN
			RDY<='1';
			COUNT<="000";
		END IF;
	END IF;
	
ELSIF RESET='1' THEN
	RDY<='1';
END IF;

END PROCESS;

END BEHAVE;