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charudatta10/FPGA_2_LCD.v

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Created April 15, 2019 07:32
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A simple character LCD controller core written in Verilog
Raw
FPGA_2_LCD.v
`timescale 1ns / 1ps
//////////////////////////////////////////////////////////////////////////////////
// Company: Carrier Frequency, Inc.
// Engineer: Jon Carrier
//
// Create Date: 21:33:11 06/17/2011
// Design Name:
// Module Name: FPGA_2_LCD
// Project Name:
// Target Devices:
// Tool versions:
// Description:
//
// Dependencies: The clock should be set to 24MHz. Slower clocks should also work.
//
// Revision:
// Revision 0.01 - File Created
// Additional Comments: This module performs the full initialization procedure.
// Once init is done, the module takes in DATA and processes
// it according to OPER. When idle, the module indicates RDY.
// ENB, indicates that DATA and OPER are valid and the module
// should start to read the lines.
// Note: the calling module must keep DATA valid until RDY re-asserts
//
//////////////////////////////////////////////////////////////////////////////////
module FPGA_2_LCD(
CLK, LCD_RS, LCD_RW, LCD_E, LCD_DB, RDY, DATA, OPER, ENB, RST
);
input CLK; // For this code to work without modification, CLK should equal 24MHz
input DATA; // The Data to send to the LCD Module
input OPER; // The Type of operation to perform (data or instruction)
input ENB; // Tells the module that the data is valid and start reading DATA and OPER
input RST;
output RDY; // Indicates that the module is Idle and ready to take more data
output LCD_RS, LCD_RW, LCD_E;
output [7:0] LCD_DB;
wire [7:0] DATA;
wire [1:0] OPER;
wire ENB;
reg RDY;
reg [7:0] LCD_DB=0;
reg LCD_RW=0; // always write to (and never read from) the LCD
reg LCD_RS=0; // HI means Data, LOW means Instruction/Command
reg LCD_E=0;
/*----------------------SOME NOTES-------------------
when RS and R/W change STATE...wait for at least 40ns ( ~1clock cycle )
after that period of time bring E high and invert E every 250ns (can be larger) ( ~6 clock cycles)
while E is HI, set DATA
when E goes LOW, maintain DATA for atleast 10ns
CLOCK=24MHz ==> 41.667ns
-------------------------END OF NOTES-------------------*/
//===============================================================================================
//------------------------------Define the Timing Parameters-------------------------------------
//===============================================================================================
parameter [19:0] t_40ns = 1; //40ns == ~1clk
parameter [19:0] t_250ns = 6; //250ns == ~6clks
parameter [19:0] t_42us = 1008; //42us == ~1008clks
parameter [19:0] t_100us = 2400; //100us == ~2400clks
parameter [19:0] t_1640us = 39360; //1.64ms == ~39360clks
parameter [19:0] t_4100us = 98400; //4.1ms == ~98400clks
parameter [19:0] t_15000us = 360000; //15ms == ~360000clks
//===============================================================================================
//------------------------------Define the BASIC Command Set-------------------------------------
//===============================================================================================
parameter [7:0] SETUP = 8'b00111000; //Execution time = 42us, sets to 8-bit interface, 2-line display, 5x7 dots
parameter [7:0] DISP_ON = 8'b00001100; //Execution time = 42us, Turn ON Display
parameter [7:0] ALL_ON = 8'b00001111; //Execution time = 42us, Turn ON All Display
parameter [7:0] ALL_OFF = 8'b00001000; //Execution time = 42us, Turn OFF All Display
parameter [7:0] CLEAR = 8'b00000001; //Execution time = 1.64ms, Clear Display
parameter [7:0] ENTRY_N = 8'b00000110; //Execution time = 42us, Normal Entry, Cursor increments, Display is not shifted
parameter [7:0] HOME = 8'b00000010; //Execution time = 1.64ms, Return Home
parameter [7:0] C_SHIFT_L = 8'b00010000; //Execution time = 42us, Cursor Shift
parameter [7:0] C_SHIFT_R = 8'b00010100; //Execution time = 42us, Cursor Shift
parameter [7:0] D_SHIFT_L = 8'b00011000; //Execution time = 42us, Display Shift
parameter [7:0] D_SHIFT_R = 8'b00011100; //Execution time = 42us, Display Shift
//===============================================================================================
//-----------------------------Create the counting mechanisms------------------------------------
//===============================================================================================
reg [19:0] cnt_timer=0; //39360 clks, used to delay the STATEmachine during a command execution (SEE above command set)
reg flag_250ns=0,flag_42us=0,flag_100us=0,flag_1640us=0,flag_4100us=0,flag_15000us=0;
reg flag_rst=1; //Start with flag RST set. so that the counting has not started
always @(posedge CLK) begin
if(flag_rst) begin
flag_250ns <= 1'b0; //Unlatch the flag
flag_42us <= 1'b0; //Unlatch the flag
flag_100us <= 1'b0; //Unlatch the flag
flag_1640us <= 1'b0; //Unlatch the flag
flag_4100us <= 1'b0; //Unlatch the flag
flag_15000us <= 1'b0; //Unlatch the flag
cnt_timer <= 20'b0;
end
else begin
if(cnt_timer>=t_250ns) begin
flag_250ns <= 1'b1;
end
else begin
flag_250ns <= flag_250ns;
end
//----------------------------
if(cnt_timer>=t_42us) begin
flag_42us <= 1'b1;
end
else begin
flag_42us <= flag_42us;
end
//----------------------------
if(cnt_timer>=t_100us) begin
flag_100us <= 1'b1;
end
else begin
flag_100us <= flag_100us;
end
//----------------------------
if(cnt_timer>=t_1640us) begin
flag_1640us <= 1'b1;
end
else begin
flag_1640us <= flag_1640us;
end
//----------------------------
if(cnt_timer>=t_4100us) begin
flag_4100us <= 1'b1;
end
else begin
flag_4100us <= flag_4100us;
end
//----------------------------
if(cnt_timer>=t_15000us) begin
flag_15000us <= 1'b1;
end
else begin
flag_15000us <= flag_15000us;
end
//----------------------------
cnt_timer <= cnt_timer + 1;
end
end
//##########################################################################################
//-----------------------------Create the STATE MACHINE------------------------------------
//##########################################################################################
reg [3:0] STATE=0;
reg [1:0] SUBSTATE=0;
always @(posedge CLK) begin
case(STATE)
//---------------------------------------------------------------------------------------
0: begin //---------------Initiate Command Sequence (RS=LOW)-----------------------------
LCD_RS <= 1'b0; //Indicate an instruction is to be sent soon
LCD_RW <= 1'b0; //Indicate a write operation
LCD_E <= 1'b0; //We are in the initial setup, keep low until 250ns has past
LCD_DB <= 8'b00000000;
RDY <= 1'b0; //Indicate that the module is busy
SUBSTATE <= 0;
if(!flag_15000us) begin //WAIT 15ms...worst case scenario
STATE <= STATE; //Remain in current STATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
STATE <= STATE+1; //Go to next STATE
flag_rst <= 1'b1; //Stop counting
end
end
//---------------------------------------------------------------------------------------
1: begin //-----------SET FUNCTION #1, 8-bit interface, 2-line display, 5x7 dots---------
LCD_RS <= 1'b0; //Indicate an instruction is to be sent soon
LCD_RW <= 1'b0; //Indicate a write operation
RDY <= 1'b0; //Indicate that the module is busy
if(SUBSTATE==0)begin
LCD_E <= 1'b0; //Disable Bus
LCD_DB <= LCD_DB; //Maintain Previous Data on the Bus
STATE <= STATE;
SUBSTATE <= 1;
end
if(SUBSTATE==1)begin
LCD_E <= 1'b1; //Enable Bus
LCD_DB <= SETUP; //Data Valid
if(!flag_250ns) begin //WAIT at least 250ns (required for LCD_E)
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
SUBSTATE <= SUBSTATE+1; //Go to next SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
if(SUBSTATE==2)begin
LCD_E <= 1'b0; //Disable Bus, Triggers LCD to read BUS
LCD_DB <= LCD_DB; //Keep Data Valid
if(!flag_4100us) begin //WAIT at least 4.1ms (required for Initialization)
STATE <= STATE; //Maintain current STATE
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
STATE <= STATE+1; //Go to next STATE
SUBSTATE <= 0; //Reset SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
end
//---------------------------------------------------------------------------------------
2: begin //-----------SET FUNCTION #2, 8-bit interface, 2-line display, 5x7 dots---------
LCD_RS <= 1'b0; //Indicate an instruction is to be sent soon
LCD_RW <= 1'b0; //Indicate a write operation
RDY <= 1'b0; //Indicate that the module is busy
if(SUBSTATE==0)begin
LCD_E <= 1'b0; //Disable Bus
LCD_DB <= LCD_DB; //Maintain Previous Data on the Bus
STATE <= STATE;
SUBSTATE <= 1;
end
if(SUBSTATE==1)begin
LCD_E <= 1'b1; //Enable Bus
LCD_DB <= SETUP; //Data Valid
if(!flag_250ns) begin //WAIT at least 250ns (required for LCD_E)
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
SUBSTATE <= SUBSTATE+1; //Go to next SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
if(SUBSTATE==2)begin
LCD_E <= 1'b0; //Disable Bus, Triggers LCD to read BUS
LCD_DB <= LCD_DB; //Keep Data Valid
if(!flag_100us) begin //WAIT at least 100us (required for Initialization)
STATE <= STATE; //Maintain current STATE
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
STATE <= STATE+1; //Go to next STATE
SUBSTATE <= 0; //Reset SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
end
//---------------------------------------------------------------------------------------
3: begin //-----------SET FUNCTION #3, 8-bit interface, 2-line display, 5x7 dots---------
LCD_RS <= 1'b0; //Indicate an instruction is to be sent soon
LCD_RW <= 1'b0; //Indicate a write operation
RDY <= 1'b0; //Indicate that the module is busy
if(SUBSTATE==0)begin
LCD_E <= 1'b0; //Disable Bus
LCD_DB <= LCD_DB; //Maintain Previous Data on the Bus
STATE <= STATE;
SUBSTATE <= 1;
end
if(SUBSTATE==1)begin
LCD_E <= 1'b1; //Enable Bus
LCD_DB <= SETUP; //Data Valid
if(!flag_250ns) begin //WAIT at least 250ns (required for LCD_E)
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
SUBSTATE <= SUBSTATE+1; //Go to next SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
if(SUBSTATE==2)begin
LCD_E <= 1'b0; //Disable Bus, Triggers LCD to read BUS
LCD_DB <= LCD_DB; //Keep Data Valid
if(!flag_100us) begin //WAIT at least 100us (required for Initialization)
STATE <= STATE; //Maintain current STATE
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
STATE <= STATE+1; //Go to next STATE
SUBSTATE <= 0; //Reset SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
end
//---------------------------------------------------------------------------------------
4: begin //-----------SET FUNCTION #4, 8-bit interface, 2-line display, 5x7 dots---------
LCD_RS <= 1'b0; //Indicate an instruction is to be sent soon
LCD_RW <= 1'b0; //Indicate a write operation
RDY <= 1'b0; //Indicate that the module is busy
if(SUBSTATE==0)begin
LCD_E <= 1'b0; //Disable Bus
LCD_DB <= LCD_DB; //Maintain Previous Data on the Bus
STATE <= STATE;
SUBSTATE <= 1;
end
if(SUBSTATE==1)begin
LCD_E <= 1'b1; //Enable Bus
LCD_DB <= SETUP; //Data Valid
if(!flag_250ns) begin //WAIT at least 250ns (required for LCD_E)
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
SUBSTATE <= SUBSTATE+1; //Go to next SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
if(SUBSTATE==2)begin
LCD_E <= 1'b0; //Disable Bus, Triggers LCD to read BUS
LCD_DB <= LCD_DB; //Keep Data Valid
if(!flag_100us) begin //WAIT at least 100us (required for Initialization)
STATE <= STATE; //Maintain current STATE
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
STATE <= STATE+1; //Go to next STATE
SUBSTATE <= 0; //Reset SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
end
//---------------------------------------------------------------------------------------
5: begin //-----------------DISPLAY, Display OFF, Cursor OFF, Blinking OFF------------------
LCD_RS <= 1'b0; //Indicate an instruction is to be sent soon
LCD_RW <= 1'b0; //Indicate a write operation
RDY <= 1'b0; //Indicate that the module is busy
if(SUBSTATE==0)begin
LCD_E <= 1'b0; //Disable Bus
LCD_DB <= LCD_DB; //Maintain Previous Data on the Bus
STATE <= STATE;
SUBSTATE <= 1;
end
if(SUBSTATE==1)begin
LCD_E <= 1'b1; //Enable Bus
LCD_DB <= ALL_OFF; //Data Valid
if(!flag_250ns) begin //WAIT at least 250ns (required for LCD_E)
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
SUBSTATE <= SUBSTATE+1; //Go to next SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
if(SUBSTATE==2)begin
LCD_E <= 1'b0; //Disable Bus, Triggers LCD to read BUS
LCD_DB <= LCD_DB; //Keep Data Valid
if(!flag_42us) begin //WAIT at least 42us (required for operation to process)
STATE <= STATE; //Maintain current STATE
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
STATE <= STATE+1; //Go to next STATE
SUBSTATE <= 0; //Reset SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
end
//---------------------------------------------------------------------------------------
6: begin //-------------------DISPLAY CLEAR, clear the display screen--------------------
LCD_RS <= 1'b0; //Indicate an instruction is to be sent soon
LCD_RW <= 1'b0; //Indicate a write operation
RDY <= 1'b0; //Indicate that the module is busy
if(SUBSTATE==0)begin
LCD_E <= 1'b0; //Disable Bus
LCD_DB <= LCD_DB; //Maintain Previous Data on the Bus
STATE <= STATE;
SUBSTATE <= 1;
end
if(SUBSTATE==1)begin
LCD_E <= 1'b1; //Enable Bus
LCD_DB <= CLEAR; //Data Valid
if(!flag_250ns) begin //WAIT at least 250ns (required for LCD_E)
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
SUBSTATE <= SUBSTATE+1; //Go to next SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
if(SUBSTATE==2)begin
LCD_E <= 1'b0; //Disable Bus, Triggers LCD to read BUS
LCD_DB <= LCD_DB; //Keep Data Valid
if(!flag_1640us) begin //WAIT at least 1640us (required for operation to process)
STATE <= STATE; //Maintain current STATE
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
STATE <= STATE+1; //Go to next STATE
SUBSTATE <= 0; //Reset SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
end
//---------------------------------------------------------------------------------------
7: begin //---------Normal ENTRY, Cursor increments, Display is not shifted--------------
LCD_RS <= 1'b0; //Indicate an instruction is to be sent soon
LCD_RW <= 1'b0; //Indicate a write operation
RDY <= 1'b0; //Indicate that the module is busy
if(SUBSTATE==0)begin
LCD_E <= 1'b0; //Disable Bus
LCD_DB <= LCD_DB; //Maintain Previous Data on the Bus
STATE <= STATE;
SUBSTATE <= 1;
end
if(SUBSTATE==1)begin
LCD_E <= 1'b1; //Enable Bus
LCD_DB <= ENTRY_N; //Data Valid
if(!flag_250ns) begin //WAIT at least 250ns (required for LCD_E)
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
SUBSTATE <= SUBSTATE+1; //Go to next SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
if(SUBSTATE==2)begin
LCD_E <= 1'b0; //Disable Bus, Triggers LCD to read BUS
LCD_DB <= LCD_DB; //Keep Data Valid
if(!flag_42us) begin //WAIT at least 42us (required for operation to process)
STATE <= STATE; //Maintain current STATE
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
STATE <= STATE+1; //Go to next STATE
SUBSTATE <= 0; //Reset SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
end
//---------------------------------------------------------------------------------------
8: begin //-----------------DISPLAY, Display ON, Cursor ON, Blinking ON------------------
LCD_RS <= 1'b0; //Indicate an instruction is to be sent soon
LCD_RW <= 1'b0; //Indicate a write operation
RDY <= 1'b0; //Indicate that the module is busy
if(SUBSTATE==0)begin
LCD_E <= 1'b0; //Disable Bus
LCD_DB <= LCD_DB; //Maintain Previous Data on the Bus
STATE <= STATE;
SUBSTATE <= 1;
end
if(SUBSTATE==1)begin
LCD_E <= 1'b1; //Enable Bus
LCD_DB <= DISP_ON;//ALL_ON; //Data Valid
if(!flag_250ns) begin //WAIT at least 250ns (required for LCD_E)
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
SUBSTATE <= SUBSTATE+1; //Go to next SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
if(SUBSTATE==2)begin
LCD_E <= 1'b0; //Disable Bus, Triggers LCD to read BUS
LCD_DB <= LCD_DB; //Keep Data Valid
if(!flag_42us) begin //WAIT at least 42us (required for operation to process)
STATE <= STATE; //Maintain current STATE
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
STATE <= STATE+1; //Go to next STATE
SUBSTATE <= 0; //Reset SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
end
//---------------------------------------------------------------------------------------
9: begin //-------------------DISPLAY CLEAR, clear the display screen--------------------
LCD_RS <= 1'b0; //Indicate an instruction is to be sent soon
LCD_RW <= 1'b0; //Indicate a write operation
RDY <= 1'b0; //Indicate that the module is busy
if(SUBSTATE==0)begin
LCD_E <= 1'b0; //Disable Bus
LCD_DB <= LCD_DB; //Maintain Previous Data on the Bus
STATE <= STATE;
SUBSTATE <= 1;
end
if(SUBSTATE==1)begin
LCD_E <= 1'b1; //Enable Bus
LCD_DB <= CLEAR; //Data Valid
if(!flag_250ns) begin //WAIT at least 250ns (required for LCD_E)
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
SUBSTATE <= SUBSTATE+1; //Go to next SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
if(SUBSTATE==2)begin
LCD_E <= 1'b0; //Disable Bus, Triggers LCD to read BUS
LCD_DB <= LCD_DB; //Keep Data Valid
if(!flag_1640us) begin //WAIT at least 1640us (required for operation to process)
STATE <= STATE; //Maintain current STATE
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
STATE <= 15; //Go to next STATE
SUBSTATE <= 0; //Reset SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
end
//---------------------------------------------------------------------------------------
10: begin//----------------------------- WRITE DATA -------------------------------------
LCD_RS <= 1'b1; //Indicate an instruction is to be sent soon
LCD_RW <= 1'b0; //Indicate a write operation
RDY <= 1'b0; //Indicate that the module is busy
if(SUBSTATE==0)begin
LCD_E <= 1'b0; //Disable Bus
LCD_DB <= LCD_DB; //Maintain Previous Data on the Bus
STATE <= STATE;
SUBSTATE <= 1;
end
if(SUBSTATE==1)begin
LCD_E <= 1'b1; //Enable Bus
LCD_DB <= DATA; //WRITE THE CHARACTER
if(!flag_250ns) begin //WAIT at least 250ns (required for LCD_E)
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
SUBSTATE <= SUBSTATE+1; //Go to next SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
if(SUBSTATE==2)begin
LCD_E <= 1'b0; //Disable Bus, Triggers LCD to read BUS
LCD_DB <= LCD_DB; //Keep Data Valid
if(!flag_250ns) begin //WAIT at least 250ns (required for LCD_E)
STATE <= STATE; //Maintain current STATE
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
STATE <= 15;//STATE+1; //Go to next STATE
SUBSTATE <= 0; //Reset SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
end
//---------------------------------------------------------------------------------------
11: begin//----------------------- WRITE INSTRUCTION ------------------------------------
LCD_RS <= 1'b0; //Indicate an instruction is to be sent soon
LCD_RW <= 1'b0; //Indicate a write operation
RDY <= 1'b0; //Indicate that the module is busy
if(SUBSTATE==0)begin
LCD_E <= 1'b0; //Disable Bus
LCD_DB <= LCD_DB; //Maintain Previous Data on the Bus
STATE <= STATE;
SUBSTATE <= 1;
end
if(SUBSTATE==1)begin
LCD_E <= 1'b1; //Enable Bus
LCD_DB <= DATA; //Data Valid
if(!flag_250ns) begin //WAIT at least 250ns (required for LCD_E)
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
SUBSTATE <= SUBSTATE+1; //Go to next SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
if(SUBSTATE==2)begin
LCD_E <= 1'b0; //Disable Bus, Triggers LCD to read BUS
LCD_DB <= LCD_DB; //Keep Data Valid
if(!flag_42us) begin //WAIT at least 49us (required for operation to process)
STATE <= STATE; //Maintain current STATE
SUBSTATE <= SUBSTATE; //Maintain current SUBSTATE
flag_rst <= 1'b0; //Start or Continue counting
end
else begin
STATE <= 15;//STATE+1; //Go to next STATE
SUBSTATE <= 0; //Reset SUBSTATE
flag_rst <= 1'b1; //Stop counting
end
end
end
//---------------------------------------------------------------------------------------
default: begin//----------This is the IDLE STATE, DO NOTHING UNTIL OPER is set-----------
LCD_RS <= LCD_RS; //Indicate an instruction is to be sent soon
LCD_RW <= 1'b0; //Indicate a write operation
LCD_DB <= LCD_DB; //Maintain Data Bus
LCD_E <= 1'b0; //Disable Bus
RDY <= 1'b1; //Indicate that the system is ready to taking in data
if(ENB==1 && RST==0)begin
case(OPER)
0:STATE<=STATE; //IDLE
1:STATE<=10; //WRITE CHARACTER
2:STATE<=11; //WRITE INSTRUCTION (assumes 49us or less time to process instr)
3:STATE<=0; //RESET
endcase
end
else if(RST==1)begin
STATE<=0;
end
end
endcase
end
endmodule
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