124 lines
2.8 KiB
Coq
124 lines
2.8 KiB
Coq
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/* pcf8574_for_HD44780.v - takes in control sequences for an HD44780 display
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and outputs data that control a pcf8574 connected to a HD44780 in a standard
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manner over i2c
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This file is part of the 9086 project.
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Copyright (c) 2023 Efthymios Kritikos
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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module pcf8574_for_HD44780(
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input wire clock,
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input wire pcf_write_req,
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input wire pcf_command_data,
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input wire [3:0]pcf_data,
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output reg pcf_busy=0,
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input new_backlight,
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input backlight_update,
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input I2C_BUSY,
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output reg I2C_SEND=0,
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output reg [7:0]i2c_data
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);
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reg backlight=1;
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reg backlight_latch=0;
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reg [3:0]pcf_state=0;
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always @(posedge clock) begin
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// [ D7 , D6 , D5 , D4 , BACKLIGHT , EN , WRITE , COMMAND/DATA ]
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if(backlight_update)
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backlight_latch<=1;
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case(pcf_state)
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4'b0000: begin /*Idle*/
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if(pcf_write_req&&I2C_BUSY==0)begin
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pcf_state<=4'b0001;
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I2C_SEND<=0;
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pcf_busy<=1;
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end else if(backlight_latch&&I2C_BUSY==0)begin
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pcf_state<=4'b1111;
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I2C_SEND<=0;
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pcf_busy<=1;
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end
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end
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4'b0001: begin
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if(I2C_BUSY==0)begin
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i2c_data<={pcf_data[3:0],backlight,1'b0,1'b0,pcf_command_data};
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I2C_SEND<=1;
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backlight_latch<=0;
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pcf_state<=4'b0010;
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end
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end
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4'b0010:begin
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if(I2C_BUSY==1)begin
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I2C_SEND<=0;
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pcf_state<=4'b0011;
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end
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end
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4'b0011: begin
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if(I2C_BUSY==0)begin
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i2c_data<={pcf_data[3:0],backlight,1'b1,1'b0,pcf_command_data};
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I2C_SEND<=1;
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backlight_latch<=0;
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pcf_state<=4'b0100;
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end
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end
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4'b0100:begin
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if(I2C_BUSY==1)begin
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I2C_SEND<=0;
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pcf_state<=4'b0101;
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end
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end
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4'b0101: begin
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if(I2C_BUSY==0)begin
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i2c_data<={pcf_data[3:0],backlight,1'b0,1'b0,pcf_command_data};
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I2C_SEND<=1;
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pcf_state<=4'b0110;
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end
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end
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4'b0110: begin
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if(I2C_BUSY==1)begin
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I2C_SEND<=0;
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pcf_state<=4'b0111;
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end
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end
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4'b0111:begin
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if(I2C_BUSY==0)begin
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pcf_state<=4'b0000;
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pcf_busy<=1'b0;
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end
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end
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4'b1111:begin
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if(I2C_BUSY==1)begin
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pcf_state<=4'b0000;
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I2C_SEND<=1'b0;
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pcf_busy<=1'b0;
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end else begin
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i2c_data<={4'b0,backlight,1'b0,1'b0,1'b0};
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backlight_latch<=0;
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I2C_SEND<=1'b1;
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pcf_busy<=1'b1;
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end
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end
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default:begin
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pcf_state<=0;
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end
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endcase
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end
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endmodule
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