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