module apb_i2c 
#(
    parameter APB_ADDR_WIDTH = 12  //APB slaves are 4KB by default
)
(
	HCLK,
	HRESETn,
	PADDR,
	PWDATA,
	PWRITE,
	PSEL,
	PENABLE,
	PRDATA,
	PREADY,
	PSLVERR,
	interrupt_o,
	scl_pad_i,
	scl_pad_o,
	scl_padoen_o,
	sda_pad_i,
	sda_pad_o,
	sda_padoen_o
);
	//parameter APB_ADDR_WIDTH = 12;
	input wire HCLK;
	input wire HRESETn;
	input wire [APB_ADDR_WIDTH - 1:0] PADDR;
	input wire [31:0] PWDATA;
	input wire PWRITE;
	input wire PSEL;
	input wire PENABLE;
	output reg [31:0] PRDATA;
	output wire PREADY;
	output wire PSLVERR;
	output reg interrupt_o;
	input wire scl_pad_i;
	output wire scl_pad_o;
	output wire scl_padoen_o;
	input wire sda_pad_i;
	output wire sda_pad_o;
	output wire sda_padoen_o;
	wire [3:0] s_apb_addr;
	reg [15:0] r_pre;
	reg [7:0] r_ctrl;
	reg [7:0] r_tx;
	wire [7:0] s_rx;
	reg [7:0] r_cmd;
	wire [7:0] s_status;
	wire s_done;
	wire s_core_en;
	wire s_ien;
	wire s_irxack;
	reg rxack;
	reg tip;
	reg irq_flag;
	wire i2c_busy;
	wire i2c_al;
	reg al;
	assign s_apb_addr = PADDR[5:2];
	always @(posedge HCLK or negedge HRESETn)
		if (~HRESETn) begin
			r_pre <= 'h0;
			r_ctrl <= 'h0;
			r_tx <= 'h0;
			r_cmd <= 'h0;
		end
		else if ((PSEL && PENABLE) && PWRITE) begin
			if (s_done | i2c_al)
				r_cmd[7:4] <= 4'h0;
			r_cmd[2:1] <= 2'b00;
			r_cmd[0] <= 1'b0;
			case (s_apb_addr)
				3'b000: r_pre <= PWDATA[15:0];
				3'b001: r_ctrl <= PWDATA[7:0];
				3'b100: r_tx <= PWDATA[7:0];
				3'b101:
					if (s_core_en)
						r_cmd <= PWDATA[7:0];
			endcase
		end
		else begin
			if (s_done | i2c_al)
				r_cmd[7:4] <= 4'h0;
			r_cmd[2:1] <= 2'b00;
			r_cmd[0] <= 1'b0;
		end
	always @(*)
		case (s_apb_addr)
			3'b000: PRDATA = {16'h0000, r_pre};
			3'b001: PRDATA = {24'h000000, r_ctrl};
			3'b010: PRDATA = {24'h000000, s_rx};
			3'b011: PRDATA = {24'h000000, s_status};
			3'b100: PRDATA = {24'h000000, r_tx};
			3'b101: PRDATA = {24'h000000, r_cmd};
			default: PRDATA = 'h0;
		endcase
	wire sta = r_cmd[7];
	wire sto = r_cmd[6];
	wire rd = r_cmd[5];
	wire wr = r_cmd[4];
	wire ack = r_cmd[3];
	wire iack = r_cmd[0];
	assign s_core_en = r_ctrl[7];
	assign s_ien = r_ctrl[6];
	i2c_master_byte_ctrl byte_controller(
		.clk(HCLK),
		.nReset(HRESETn),
		.ena(s_core_en),
		.clk_cnt(r_pre),
		.start(sta),
		.stop(sto),
		.read(rd),
		.write(wr),
		.ack_in(ack),
		.din(r_tx),
		.cmd_ack(s_done),
		.ack_out(s_irxack),
		.dout(s_rx),
		.i2c_busy(i2c_busy),
		.i2c_al(i2c_al),
		.scl_i(scl_pad_i),
		.scl_o(scl_pad_o),
		.scl_oen(scl_padoen_o),
		.sda_i(sda_pad_i),
		.sda_o(sda_pad_o),
		.sda_oen(sda_padoen_o)
	);
	always @(posedge HCLK or negedge HRESETn)
		if (!HRESETn) begin
			al <= 1'b0;
			rxack <= 1'b0;
			tip <= 1'b0;
			irq_flag <= 1'b0;
		end
		else begin
			al <= i2c_al | (al & ~sta);
			rxack <= s_irxack;
			tip <= rd | wr;
			irq_flag <= ((s_done | i2c_al) | irq_flag) & ~iack;
		end
	always @(posedge HCLK or negedge HRESETn)
		if (!HRESETn)
			interrupt_o <= 1'b0;
		else
			interrupt_o <= irq_flag && s_ien;
	assign s_status[7] = rxack;
	assign s_status[6] = i2c_busy;
	assign s_status[5] = al;
	assign s_status[4:2] = 3'h0;
	assign s_status[1] = tip;
	assign s_status[0] = irq_flag;
	assign PREADY = 1'b1;
	assign PSLVERR = 1'b0;
endmodule