El planteamiento de esta entrada es si podemos hacer una verificación física del RISC-V, en la placa DE2-115 mediante el LCD.
La controladora verilog de LCD proviene de la siguiente dirección y autoría:
https://gist.github.com/windhooked/40f6c9a6d35062a5d24503d2bcb07ddd
La adaptación que he realizado ha consistido fundamentalmente en generar una salida adicional que resetee el micro RISC-V mientras el LCD arranca, de forma que cuando esté el LCD inicializado, liberemos el micro RISC-V y pueda empezar a ejecutar sus instrucciones. Esa salida adicional se denomina RST_output.
Otro cambio que introduje fue un enable general denominado TC_general de un contador módulo 20 que nos garantice que los niveles a 1 de LCD_E sean superiores a 400 ns (trabajamos con un reloj de 50 MHz), aunque cómo veréis he multiplicado por 20 todas las temporizaciones y solo así he conseguido que funcionara.
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module FPGA_2_LCD_RAFA( CLK, LCD_RS, LCD_RW, LCD_E, LCD_DB, RDY, DATA, OPER, ENB, RST, RST_output ); input CLK; // For this code to work without modification, CLK should equal 24MHz input [7:0] DATA; // The Data to send to the LCD Module input [1:0] 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 RST_output; output LCD_RS, LCD_RW, LCD_E; output [7:0] LCD_DB; reg RST_output; 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 20ns ( ~1clock cycle ) after that period of time bring E high and invert E every 400 ns (can be larger) ( ~20 clock cycles) while E is HI, set DATA when E goes LOW, maintain DATA for atleast 10ns CLOCK=50MHz ==> 20 ns -------------------------END OF NOTES-------------------*/ //=============================================================================================== //------------------------------Define the Timing Parameters------------------------------------- //=============================================================================================== parameter [19:0] t_40ns = 1; //20ns == ~1clk parameter [19:0] t_250ns = 6; //400ns == ~20clks parameter [19:0] t_42us = 1008; //21us == ~1008clks parameter [19:0] t_100us = 2400; //50us == ~2400clks parameter [19:0] t_1640us = 39360; //0.82ms == ~39360clks parameter [19:0] t_4100us = 98400; //2.05ms == ~98400clks parameter [19:0] t_15000us = 360000; //7,5ms == ~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 reg flag_40ns; reg [4:0] idea; wire TC_general; assign TC_general=(idea==5'b10011)?1'b1:1'b0; always @(posedge CLK, negedge RST) begin if (!RST) begin flag_40ns <=1'b0; 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; idea<=5'b00000; end else begin if (idea==5'b10011) idea<=5'b00000; else idea<=idea+1; if (TC_general) if(flag_rst ) begin flag_40ns <=1'b0; 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 flag_40ns<= cnt_timer[0]; //si el reloj es de 50 MHz , esta señal es de 25 MHz 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 end //########################################################################################## //-----------------------------Create the STATE MACHINE------------------------------------ //########################################################################################## reg [3:0] STATE; reg [1:0] SUBSTATE; always @(posedge CLK, negedge RST) begin if (!RST) begin 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; STATE<=0; flag_rst <= 1'b0; RST_output <=1'b0; end else if (TC_general) 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; flag_rst <= 1'b1; 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&& !flag_rst) begin STATE <= 15;//STATE+1; //Go to next STATE SUBSTATE <= 0; //Reset SUBSTATE flag_rst <= 1'b1; end else 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 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; RST_output <=1'b1; //Indicate that the system is ready to taking in data if(ENB==1)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 end endcase end endmodule |
