/* CPU_to_I2C_driver_bridge - Implements CPU interface for the I2C_driver

   This file is part of the 9086 project.

   Copyright (c) 2024 Efthymios Kritikos

   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 CPU_to_I2C_driver_bridge (
	input wire clock,
	input wire reset_n,

	// CPU INTERFACE
	input wire [2:0] address,
	input wire [15:0] data_bus_in,
	output reg [15:0] data_bus_out,
	input read_n,
	input write_n,
	input chip_select_n,

	// I2C DRIVER INTERFACE
	output wire [6:0] OUT_ADDRESS,
	input wire OUT_BUSY,
	output reg OUT_TRANSACT,
	output reg DIR,
	input wire [15:0] OUT_I2C_DATA_READ,
	output reg [15:0] OUT_I2C_DATA_WRITE,

	output reg TRANS_WIDTH,
	output reg OUT_IGN_ACK,

	input IN_ERROR
);

//assign data_bus_out=((address==3'h0)&&chip_select_n==1'b0&&read_n==1'b0)? 16'h0043 : 16'h0000;
//assign data_bus_out= (chip_select_n==1'b0&&read_n==1'b0) ? 16'h0043 : 16'h0000;
//assign data_bus_out= (1) ? 16'h0043 : 16'h0000;

reg [6:0] ADDRESS_REG=7'b1111111;

assign OUT_ADDRESS=ADDRESS_REG;

/* verilator lint_off UNUSEDSIGNAL */
reg [15:0]READ_DATA=16'h0;
/* verilator lint_on UNUSEDSIGNAL */

reg WAIT;
always @( posedge clock )begin
	if ( reset_n==0 ) begin
		WAIT<=0;
		OUT_TRANSACT<=0;
	end
	if ( WAIT==1'b1 && OUT_BUSY==1'b1 )begin
		WAIT<=1'b0;
		OUT_TRANSACT<=0;
		READ_DATA<=OUT_I2C_DATA_READ;
	end
	if ( chip_select_n==0 && read_n==0 )begin
		case (address)
			3'h0: data_bus_out <= {OUT_I2C_DATA_READ};
			3'h2: data_bus_out <= {14'd0,IN_ERROR,OUT_BUSY|WAIT};
			default: data_bus_out <= 16'h0;
		endcase
	end
	if ( chip_select_n==0 && write_n==0 && address==3'd3 ) begin
		OUT_TRANSACT<=1;
		WAIT<=1;
	end
	if ( chip_select_n==0 && write_n==0 && address==3'd3 ) begin
		DIR<=data_bus_in[8:8];
		TRANS_WIDTH<=data_bus_in[9:9];
		OUT_IGN_ACK<=data_bus_in[10:10];
	end
	if ( chip_select_n==0 && write_n==0 && address==3'd1 ) begin
		ADDRESS_REG <= data_bus_in[14:8];
	end
	if ( chip_select_n==0 && write_n==0 && address==3'd2 ) begin
		OUT_I2C_DATA_WRITE <= data_bus_in[15:0];
	end
end

endmodule