path: root/src/rtl/modexps6_wrapper.v

module modexps6_wrapper
	(
		clk, reset_n,
		cs, we,
		address, write_data, read_data
	);
	
	
		//
		// Ports
		//
	input		wire           clk;
	input		wire           reset_n;

	input		wire           cs;
	input		wire           we;

	input		wire  [ 9: 0]	address;
	input		wire  [31: 0]	write_data;
	output	wire	[31: 0]	read_data;
	
	
		//
		// Address Decoder
		//
	localparam	ADDR_MSB_REGS	= 1'b0;
	localparam	ADDR_MSB_CORE	= 1'b1;
	wire				address_msb = address[9];
	wire	[ 8: 0]	address_lsb	= address[8:0];
	
	
		//
		// Output Mux
		//
	wire	[31: 0]	read_data_regs;
	wire	[31: 0]	read_data_core;
	
	
	  //
	  // Registers
	  //
	localparam ADDR_NAME0			= 9'h000;
	localparam ADDR_NAME1			= 9'h001;
	localparam ADDR_VERSION			= 9'h002;

	localparam ADDR_CONTROL			= 9'h008;		// {next, init}
	localparam ADDR_STATUS			= 9'h009;		// {valid, ready}
	localparam ADDR_MODE				= 9'h010;		// 0 = slow secure, 1 = fast unsafe (public)
	localparam ADDR_MODULUS_BITS	= 9'h011;		// 
	localparam ADDR_EXPONENT_BITS	= 9'h012;		// 
	localparam ADDR_GPIO_REG		= 9'h020;		// 

	localparam CONTROL_INIT_BIT	= 0;
	localparam CONTROL_NEXT_BIT	= 1;

	localparam STATUS_READY_BIT	= 0;
	localparam STATUS_VALID_BIT	= 1;

	localparam CORE_NAME0			= 32'h6D6F6465;	// "mode"
	localparam CORE_NAME1			= 32'h78707336;	// "xps6"
	localparam CORE_VERSION			= 32'h302E3130;	// "0.10"


		//
		// Registers
		//
	reg	[ 1: 0]	reg_control;
	reg				reg_mode;
	reg	[12: 0]	reg_modulus_width;
	reg	[12: 0]	reg_exponent_width;
	reg	[31: 0]	reg_gpio;
	
	
		//
		// Wires
		//
	wire	[ 1: 0]	reg_status;
		
		
		//
		// ModExpS6
		//
	modexps6_top #
	(
		.MAX_MODULUS_WIDTH	(4096)
	)
	modexps6_core
	(
		.clk						(clk),
		
		.init						(reg_control[CONTROL_INIT_BIT]),
		.ready					(reg_status[STATUS_READY_BIT]),
		.next						(reg_control[CONTROL_NEXT_BIT]),
		.valid					(reg_status[STATUS_VALID_BIT]),
		
		.modulus_width			(reg_modulus_width),
		.exponent_width		(reg_exponent_width),
		
		.fast_public_mode		(reg_mode),
		
		.bus_cs					(cs && (address_msb == ADDR_MSB_CORE)),
		.bus_we					(we),
		.bus_addr				(address_lsb),
		.bus_data_wr			(write_data),
		.bus_data_rd			(read_data_core)
	);
	
	
		//
		// Read Latch
		//
	reg [31: 0] tmp_read_data;


	//
	// Read/Write Interface
	//
	always @(posedge clk)
		//
		if (!reset_n) begin
			//
			reg_control				<= 2'b00;
			reg_mode					<= 1'b0;
			reg_modulus_width		<= 13'd1024;
			reg_exponent_width	<= 13'd1024;
			//
		end else if (cs && (address_msb == ADDR_MSB_REGS)) begin
			//
			if (we) begin
				//
				// Write Handler
				//
				case (address_lsb)
					//
					ADDR_CONTROL:			reg_control				<= write_data[ 1: 0];
					ADDR_MODE:				reg_mode					<= write_data[0];
					ADDR_MODULUS_BITS:	reg_modulus_width		<= write_data[12: 0];
					ADDR_EXPONENT_BITS:	reg_exponent_width	<= write_data[12: 0];
					ADDR_GPIO_REG:			reg_gpio					<= write_data;
					//
				endcase
				//	
			end else begin
				//
				// Read Handler
				//
				case (address)
					//
					ADDR_NAME0:				tmp_read_data <= CORE_NAME0;
					ADDR_NAME1:				tmp_read_data <= CORE_NAME1;
					ADDR_VERSION:			tmp_read_data <= CORE_VERSION;
					ADDR_CONTROL:			tmp_read_data <= {{30{1'b0}}, reg_control};
					ADDR_STATUS:			tmp_read_data <= {{30{1'b0}}, reg_status};
					ADDR_MODE:				tmp_read_data <= {{31{1'b0}}, reg_mode};
					ADDR_MODULUS_BITS:	tmp_read_data <= {{19{1'b0}}, reg_modulus_width};
					ADDR_EXPONENT_BITS:	tmp_read_data <= {{19{1'b0}}, reg_exponent_width};
					ADDR_GPIO_REG:			tmp_read_data <= reg_gpio;
					//
					default:					tmp_read_data <= 32'h00000000;
					//
				endcase
				//
			end
			//
		end
		
		
		//
		// Register / Core Memory Selector
		//
	reg address_msb_last;
	always @(posedge clk) address_msb_last = address_msb;
	
	reg	[31: 0]	read_data_mux;
	assign read_data = read_data_mux;	
	
	always @(*)
		//
		case (address_msb_last)
			//
			ADDR_MSB_REGS:		read_data_mux = tmp_read_data;
			ADDR_MSB_CORE:		read_data_mux = read_data_core;
			//
		endcase

		
endmodule