Subversion Repositories xilinx_virtex_fp_library

`timescale 1ns / 1ps
//////////////////////////////////////////////////////////////////////////////////
// Company: 	UPT
// Engineer: 	Constantina-Elena Gavriliu
// 
// Create Date:    16:09:49 11/04/2013 
// Design Name: 
// Module Name:    SinglePathFPAdder 
 
// Project Name: 
// Target Devices: 
// Tool versions: 
// Description: A ± B
//				//do not take into consideration cases for which the operation generates a NaN or Infinity exception (with corresponding sign) when initial "special cases" are not such exceptions
//
// Dependencies: 	effective_op.v
//					leading_zeros.v
//					rounding.v
//					shifter.v
//					special_cases.v
//
// Revision: 
// Revision 0.01 - File Created
// Additional Comments: 
//
//////////////////////////////////////////////////////////////////////////////////
module SinglePathFPAdder #(	parameter size_mantissa 			= 24, //calculate the size containing the hiden bit 1.M
							parameter size_exponent 			= 8,
							parameter size_exception_field		= 2,
							parameter size_counter				= 5,	//log2(size_mantissa) + 1 = 5)
							parameter [size_exception_field - 1 : 0] zero			= 0, //00
							parameter [size_exception_field - 1 : 0] normal_number	= 1, //01
							parameter [size_exception_field - 1 : 0] infinity		= 2, //10
							parameter [size_exception_field - 1 : 0] NaN			= 3, //11
							parameter pipeline					= 0,
							parameter pipeline_pos				= 0,	// 8 bits
							parameter double_size_mantissa		= size_mantissa + size_mantissa,
							parameter double_size_counter		= size_counter + 1,
							parameter size	= size_mantissa + size_exponent + size_exception_field)
 
						(	input sub,
							input [size - 1 : 0] a_number_i,
							input [size - 1 : 0] b_number_i,
							output[size - 1 : 0] resulted_number_o);
 
 
	wire [size_exception_field - 1 : 0] sp_case_a_number, sp_case_b_number; 
	wire [size_mantissa - 1 : 0] m_a_number, m_b_number;
	wire [size_exponent - 1 : 0] e_a_number, e_b_number;
	wire s_a_number, s_b_number;
 
	wire [size_exponent     : 0] a_greater_exponent, b_greater_exponent;
	wire [size_exponent - 1 : 0] unadjusted_exponent;
	wire [1 : 0] adjust_exponent;
 
	wire [size_exponent - 1 : 0] exp_difference;
	wire [size_exponent     : 0] exp_inter;
	wire [size_mantissa - 1 : 0] shifted_m_b;
	wire [size_mantissa - 1 : 0] initial_rounding_bits, final_rounding_bits;
	wire [size_mantissa - 2 : 0] inter_rounding_bits;
	wire eff_op;
 
	wire [size_counter  - 1 : 0] lzs;
	wire [size_mantissa + 2	: 0] adder_mantissa;
	wire [size_mantissa 	: 0] rounded_mantissa;
	wire [size_mantissa + 1	: 0] unnormalized_mantissa;
	wire [size_mantissa - 1 : 0] unrounded_mantissa;
 
	wire [size_exception_field - 1 : 0] resulted_exception_field;
	wire [size_mantissa - 1	: 0] resulted_mantissa;
	wire [size_exponent - 1 : 0] resulted_exponent;
	wire resulted_sign;
 
	wire [1:0] dummy_bits;
	wire zero_flag;
	wire [4:0] sign_cases;
	wire dummy_ovf, correction, negation_cond;
	reg intermediar_sign;
 
 
	assign e_a_number	= a_number_i[size_mantissa + size_exponent - 1 : size_mantissa - 1];
	assign e_b_number = b_number_i[size_mantissa + size_exponent - 1 : size_mantissa - 1];
	assign s_a_number = a_number_i[size - size_exception_field - 1];
	assign s_b_number = b_number_i[size - size_exception_field - 1];
	assign sp_case_a_number = a_number_i[size - 1 : size - size_exception_field];
	assign sp_case_b_number = b_number_i[size - 1 : size - size_exception_field];
 
	//find the greater exponent
	assign a_greater_exponent = e_a_number - e_b_number;
	assign b_greater_exponent = e_b_number - e_a_number;
 
	//find the difference between exponents
	assign exp_difference 	= (a_greater_exponent[size_exponent])? b_greater_exponent[size_exponent - 1 : 0] : a_greater_exponent[size_exponent - 1 : 0];
	assign exp_inter 		= (b_greater_exponent[size_exponent])? {1'b0, e_a_number} : {1'b0, e_b_number};
 
	//set shifter always on m_b_number
	assign {m_a_number, m_b_number} = (b_greater_exponent[size_exponent])? 
													{{1'b1, a_number_i[size_mantissa - 2 :0]}, {1'b1, b_number_i[size_mantissa - 2 :0]}} : 
													{{1'b1, b_number_i[size_mantissa - 2 :0]}, {1'b1, a_number_i[size_mantissa - 2 :0]}};				
	//shift m_b_number				
	shifter #(	.INPUT_SIZE(size_mantissa),
				.SHIFT_SIZE(size_exponent),
				.OUTPUT_SIZE(double_size_mantissa),
				.DIRECTION(1'b0), //0=right, 1=left
				.PIPELINE(pipeline),
				.POSITION(pipeline_pos))
		m_b_shifter_instance(	.a(m_b_number),//mantissa
								.arith(1'b0),//logical shift
								.shft(exp_difference),
								.shifted_a({shifted_m_b, initial_rounding_bits}));
 
	//istantiate effective_operation_component
	effective_op effective_op_instance( .a_sign(s_a_number), .b_sign(s_b_number), .sub(sub), .eff_op(eff_op));
 
	//compute addition
	assign adder_mantissa = (eff_op)? 	({1'b0, m_a_number, 1'b0} - {1'b0, shifted_m_b, initial_rounding_bits[size_mantissa - 1]}) : 
										({1'b0, m_a_number, 1'b0} + {1'b0, shifted_m_b, initial_rounding_bits[size_mantissa - 1]});
 
	//compute unnormalized_mantissa
	assign unnormalized_mantissa = (adder_mantissa[size_mantissa + 2])? ~adder_mantissa[size_mantissa + 1 : 0] : adder_mantissa[size_mantissa + 1 : 0];
 
	assign inter_rounding_bits = (~(|exp_difference[size_exponent - 1 : 1]))?
											((adder_mantissa[size_mantissa + 2]? ~initial_rounding_bits[size_mantissa - 2 : 0] : initial_rounding_bits[size_mantissa - 2 : 0])) : 
											((eff_op)? ((|initial_rounding_bits[size_mantissa - 2 : 0])?~initial_rounding_bits[size_mantissa - 2 : 0] : initial_rounding_bits[size_mantissa - 2 : 0]) : initial_rounding_bits[size_mantissa - 2 : 0]);
 
	//compute leading_zeros over unnormalized mantissa
	leading_zeros #(	.SIZE_INT(size_mantissa + 2), .SIZE_COUNTER(size_counter), .PIPELINE(pipeline))
		leading_zeros_instance (.a(unnormalized_mantissa[size_mantissa + 1 : 0]), 
										.ovf(unnormalized_mantissa[size_mantissa + 1]), 
										.lz(lzs));
 
	//compute shifting over unnormalized_mantissa
	shifter #(	.INPUT_SIZE(double_size_mantissa + 1),
					.SHIFT_SIZE(size_counter),
					.OUTPUT_SIZE(double_size_mantissa + 2),
					.DIRECTION(1'b1), //0=right, 1=left
					.PIPELINE(pipeline),
					.POSITION(pipeline_pos))
		shifter_instance(	.a({unnormalized_mantissa, inter_rounding_bits}),//mantissa
								.arith(inter_rounding_bits[0]),//logical shift
								.shft(lzs),
								.shifted_a({unrounded_mantissa, final_rounding_bits, dummy_bits}));
 
	assign correction = ~(|exp_difference[size_exponent - 1 : 1])? 	1'b0 : 
							(eff_op? ((|initial_rounding_bits[size_mantissa - 2 : 0])? 
								((adder_mantissa[0] | ((~adder_mantissa[0]) & (~adder_mantissa[size_mantissa]) & (~initial_rounding_bits[size_mantissa - 1]) 
										& (~(&final_rounding_bits[size_mantissa-2 : 0]))))? 1'b1 : 1'b0) : 1'b0) : 1'b0);
 
	//instantiate rounding_component
	rounding #(	.SIZE_MOST_S_MANTISSA(size_mantissa + 1),
				.SIZE_LEAST_S_MANTISSA(size_mantissa))
		rounding_instance(	.unrounded_mantissa({1'b0, unrounded_mantissa}),
		                    .dummy_bits(final_rounding_bits),
							.eff_op(eff_op),
							.correction(correction),
		                    .rounded_mantissa(rounded_mantissa));
 
	//adjust exponent in case of overflow
	assign adjust_exponent = (rounded_mantissa[size_mantissa])? 2'd2 : 2'd1;
 
	//compute resulted_exponent
	assign unadjusted_exponent = exp_inter - lzs;
	assign resulted_exponent = unadjusted_exponent + adjust_exponent;
 
	assign resulted_mantissa = (rounded_mantissa[size_mantissa])? (rounded_mantissa[size_mantissa : 1]) : (rounded_mantissa[size_mantissa - 1 : 0]);
 
	//compute exception_field
	special_cases	#(	.size_exception_field(size_exception_field),
							.zero(zero), 
							.normal_number(normal_number),
							.infinity(infinity),
							.NaN(NaN))
		special_cases_instance( .sp_case_a_number(sp_case_a_number),
										.sp_case_b_number(sp_case_b_number),
										.eff_op(eff_op),
										.sp_case_result_o(resulted_exception_field)); 
 
	//set zero_flag in case of equal numbers
	assign zero_flag = ~((|{resulted_mantissa,resulted_exception_field[1]}) & (|resulted_exception_field));
 
	assign sign_cases = {eff_op, s_a_number, s_b_number, a_greater_exponent[size_exponent], b_greater_exponent[size_exponent]};
 
	always 
		@(*)
	begin
		case (sign_cases)
			5'b00000:	intermediar_sign = 1'b0;
			5'b00001:	intermediar_sign = 1'b0;
			5'b00010:	intermediar_sign = 1'b0;
 
			5'b10000:	intermediar_sign = ~adder_mantissa[size_mantissa+1];
			5'b10001:	intermediar_sign = 1'b0;
			5'b10010:	intermediar_sign = 1'b1;
 
			5'b10100:	intermediar_sign = ~adder_mantissa[size_mantissa+1];
			5'b10101:	intermediar_sign = 1'b0;
			5'b10110:	intermediar_sign = 1'b1;
 
			5'b00100:	intermediar_sign = 1'b0;
			5'b00101:	intermediar_sign = 1'b0;
			5'b00110:	intermediar_sign = 1'b0;
 
			5'b11000:	intermediar_sign = adder_mantissa[size_mantissa+1];
			5'b11001:	intermediar_sign = 1'b1;
			5'b11010:	intermediar_sign = 1'b0;
 
			5'b01000:	intermediar_sign = 1'b1;
			5'b01001:	intermediar_sign = 1'b1;
			5'b01010:	intermediar_sign = 1'b1;
 
			5'b01100:	intermediar_sign = 1'b1;
			5'b01101:	intermediar_sign = 1'b1;
			5'b01110:	intermediar_sign = 1'b1;
 
			5'b11100:	intermediar_sign = adder_mantissa[size_mantissa+1];
			5'b11101:	intermediar_sign = 1'b1;
			5'b11110:	intermediar_sign = 1'b0;
 
			default: intermediar_sign = 1'b1;
		endcase
	end
 
	assign resulted_sign = intermediar_sign;
 
	assign resulted_number_o = (zero_flag | (~(|resulted_exception_field)))? {size{1'b0}} :
									(&(resulted_exception_field))? {resulted_exception_field, resulted_sign,{(size-1-size_exception_field){1'b0}}} :
									(resulted_exception_field[1])? {resulted_exception_field, {(size-size_exception_field){1'b0}}} :
									(!sp_case_a_number)? {b_number_i[size-1 : size-size_exception_field], resulted_sign, b_number_i[size-1-size_exception_field-1 : 0]} :
									(!sp_case_b_number)? {a_number_i[size-1 : size-size_exception_field], resulted_sign, a_number_i[size-1-size_exception_field-1 : 0]} :
									{resulted_exception_field, resulted_sign, resulted_exponent, resulted_mantissa[size_mantissa - 2 : 0]};
 
endmodule