Subversion Repositories 16x2_lcd_display_driver

/*
16x2 LCD DRIVER
DESCRIPTION
	Driver for 16X2 LCD.
	Fetch data from the input data port and presents it to the LCD pins with enable latch pulse. cd input pin 
	is used to select whether the data is lcd command data or character data. 
IO DETAILS
  	data	>>	lcd input
	clk		>>	Clock
	rst		>>	Reset
	start	>>	Start process
	cd		>> 	0-LCD Command/1-LCD Char
	rs		>>	LCD Register select
	en		>>	LCD Enable
	done_tick	>>	Process completed clock tick
AUTHOR:	
	Name:	Jagadeesh J
	Email:	jagadeeshj@kenosys.in
	Tel:	+91-8098701730	
COMPANY:
	KENOSYS EMBEDDED SOLUTIONS, SALEM, TAMILNADU, INDIA			
 
 This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
 
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
 
   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 */
 module lcd_16x2_8bit (
	input [7:0]data,			
	input clk, rst, start, cd,	
	output [7:0]lcd_data,
	output rs, en, 
	output reg done_tick
);
 
localparam [2:0]	idle	=	3'b000,
					load	=	3'b001,
					wait1	=	3'b010,
					wait2 	= 	3'b011,
					done	=	3'b100;
 
reg [2:0]state_reg,state_next;
reg [15:0]count_reg;
wire [15:0]count_next;
reg [7:0]lcd_data_reg, lcd_data_next;
reg rs_reg, rs_next, en_reg, en_next, c_load_reg, c_load_next;
wire c_1ms, c_h1ms;
 
always@(posedge clk, negedge rst)
begin
	if(!rst)
	begin
		state_reg <= idle;
		c_load_reg <= 0;
		en_reg <= 0;
		rs_reg <= 0;
		lcd_data_reg <= 0;
		count_reg <= 0;
	end
	else
	begin
		state_reg <= state_next;
		c_load_reg <= c_load_next;
		en_reg <= en_next;
		rs_reg <= rs_next;
		lcd_data_reg <= lcd_data_next;
		count_reg <= count_next;
	end
end
 
assign count_next = (c_load_reg)?(count_reg + 1'b1):16'd0;
 
assign c_1ms = (count_reg == 16'd50000);
assign c_h1ms = (count_reg == 16'd25000);
 
always@*
begin
	state_next = state_reg;
	rs_next = rs_reg;
	en_next = en_reg;
	lcd_data_next = lcd_data_reg;
	done_tick = 0;
	c_load_next = c_load_reg;
	case(state_reg)
		idle:
		begin
			if(start)
				state_next = load;
		end
		load:
		begin
			state_next = wait1;
			lcd_data_next = data;
			rs_next = cd;
		end
		wait1:
		begin
			c_load_next = 1;
			en_next = 1;
			if(c_1ms)
			begin
				state_next = wait2;
				en_next = 0;
				c_load_next = 0;
			end
		end
		wait2:
		begin
			c_load_next= 1;
			if(c_h1ms)
			begin
				state_next = done;
				c_load_next = 0;
			end
		end
		done:
		begin
			done_tick = 1;
			state_next = idle;
		end
endcase
end
assign lcd_data = lcd_data_reg;
assign en = en_reg;
assign rs = rs_reg;
endmodule