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//////////////////////////////////////////////////////////////////////
////                                                              ////
////  OR1200's Top level multiplier, divider and MAC              ////
////                                                              ////
////  This file is part of the OpenRISC 1200 project              ////
////  http://opencores.org/project,or1k                           ////
////                                                              ////
////  Description                                                 ////
////  Multiplier is 32x32 however multiply instructions only      ////
////  use lower 32 bits of the result. MAC is 32x32=64+64.        ////
////                                                              ////
////  To Do:                                                      ////
////   - make signed division better, w/o negating the operands   ////
////                                                              ////
////  Author(s):                                                  ////
////      - Damjan Lampret, lampret@opencores.org                 ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
////                                                              ////
//// Copyright (C) 2000 Authors and OPENCORES.ORG                 ////
////                                                              ////
//// This source file may be used and distributed without         ////
//// restriction provided that this copyright statement is not    ////
//// removed from the file and that any derivative work contains  ////
//// the original copyright notice and the associated disclaimer. ////
////                                                              ////
//// This source file is free software; you can redistribute it   ////
//// and/or modify it under the terms of the GNU Lesser General   ////
//// Public License as published by the Free Software Foundation; ////
//// either version 2.1 of the License, or (at your option) any   ////
//// later version.                                               ////
////                                                              ////
//// This source 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 Lesser General Public License for more ////
//// details.                                                     ////
////                                                              ////
//// You should have received a copy of the GNU Lesser General    ////
//// Public License along with this source; if not, download it   ////
//// from http://www.opencores.org/lgpl.shtml                     ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
//
// CVS Revision History
//
// $Log: or1200_mult_mac.v,v $
// Revision 2.0  2010/06/30 11:00:00  ORSoC
// Minor update: 
// Bugs fixed. 
//
 
// synopsys translate_off
`include "timescale.v"
// synopsys translate_on
`include "or1200_defines.v"
 
module or1200_mult_mac(
	// Clock and reset
	clk, rst,
 
	// Multiplier/MAC interface
	ex_freeze, id_macrc_op, macrc_op, a, b, mac_op, alu_op, result, mac_stall_r,
 
	// SPR interface
	spr_cs, spr_write, spr_addr, spr_dat_i, spr_dat_o
);
 
parameter width = `OR1200_OPERAND_WIDTH;
 
//
// I/O
//
 
//
// Clock and reset
//
input				clk;
input				rst;
 
//
// Multiplier/MAC interface
//
input				ex_freeze;
input				id_macrc_op;
input				macrc_op;
input	[width-1:0]		a;
input	[width-1:0]		b;
input	[`OR1200_MACOP_WIDTH-1:0]	mac_op;
input	[`OR1200_ALUOP_WIDTH-1:0]	alu_op;
output	[width-1:0]		result;
output				mac_stall_r;
 
//
// SPR interface
//
input				spr_cs;
input				spr_write;
input	[31:0]			spr_addr;
input	[31:0]			spr_dat_i;
output	[31:0]			spr_dat_o;
 
//
// Internal wires and regs
//
`ifdef OR1200_MULT_IMPLEMENTED
reg	[width-1:0]		result;
reg	[2*width-1:0]		mul_prod_r;
`else
wire	[width-1:0]		result;
wire	[2*width-1:0]		mul_prod_r;
`endif
wire	[2*width-1:0]		mul_prod;
wire	[`OR1200_MACOP_WIDTH-1:0]	mac_op;
`ifdef OR1200_MAC_IMPLEMENTED
reg	[`OR1200_MACOP_WIDTH-1:0]	mac_op_r1;
reg	[`OR1200_MACOP_WIDTH-1:0]	mac_op_r2;
reg	[`OR1200_MACOP_WIDTH-1:0]	mac_op_r3;
reg				mac_stall_r;
reg	[2*width-1:0]		mac_r;
`else
wire	[`OR1200_MACOP_WIDTH-1:0]	mac_op_r1;
wire	[`OR1200_MACOP_WIDTH-1:0]	mac_op_r2;
wire	[`OR1200_MACOP_WIDTH-1:0]	mac_op_r3;
wire				mac_stall_r;
wire	[2*width-1:0]		mac_r;
`endif
wire	[width-1:0]		x;
wire	[width-1:0]		y;
wire				spr_maclo_we;
wire				spr_machi_we;
wire				alu_op_div_divu;
wire				alu_op_div;
reg				div_free;
`ifdef OR1200_DIV_IMPLEMENTED
wire	[width-1:0]		div_tmp;
reg	[5:0]			div_cntr;
`endif
 
//
// Combinatorial logic
//
`ifdef OR1200_MAC_IMPLEMENTED
assign spr_maclo_we = spr_cs & spr_write & spr_addr[`OR1200_MAC_ADDR];
assign spr_machi_we = spr_cs & spr_write & !spr_addr[`OR1200_MAC_ADDR];
assign spr_dat_o = spr_addr[`OR1200_MAC_ADDR] ? mac_r[31:0] : mac_r[63:32];
`else
assign spr_maclo_we = 1'b0;
assign spr_machi_we = 1'b0;
assign spr_dat_o = 32'h0000_0000;
`endif
`ifdef OR1200_LOWPWR_MULT
assign x = (alu_op_div & a[31]) ? ~a + 1'b1 : 
	   alu_op_div_divu | (alu_op == `OR1200_ALUOP_MUL) | (|mac_op) ? 
	   a : 32'h0000_0000;
assign y = (alu_op_div & b[31]) ? ~b + 1'b1 : 
	   alu_op_div_divu | (alu_op == `OR1200_ALUOP_MUL) | (|mac_op) ? 
	   b : 32'h0000_0000;
`else
assign x = alu_op_div & a[31] ? ~a + 32'b1 : a;
assign y = alu_op_div & b[31] ? ~b + 32'b1 : b;
`endif
`ifdef OR1200_DIV_IMPLEMENTED
assign alu_op_div = (alu_op == `OR1200_ALUOP_DIV);
assign alu_op_div_divu = alu_op_div | (alu_op == `OR1200_ALUOP_DIVU);
assign div_tmp = mul_prod_r[63:32] - y;
`else
assign alu_op_div = 1'b0;
assign alu_op_div_divu = 1'b0;
`endif
 
`ifdef OR1200_MULT_IMPLEMENTED
 
//
// Select result of current ALU operation to be forwarded
// to next instruction and to WB stage
//
always @(alu_op or mul_prod_r or mac_r or a or b)
  casex(alu_op)	// synopsys parallel_case
 `ifdef OR1200_DIV_IMPLEMENTED
    `OR1200_ALUOP_DIV: begin
       result = a[31] ^ b[31] ? ~mul_prod_r[31:0] + 1'b1 : mul_prod_r[31:0];
    end
    `OR1200_ALUOP_DIVU,
 `endif
    `OR1200_ALUOP_MUL: begin
       result = mul_prod_r[31:0];
    end
    default:
 `ifdef OR1200_MAC_SHIFTBY
      result = mac_r[`OR1200_MAC_SHIFTBY+31:`OR1200_MAC_SHIFTBY];
 `else
      result = mac_r[31:0];
 `endif
  endcase
 
   //
   // Instantiation of the multiplier
   //
 `ifdef OR1200_ASIC_MULTP2_32X32
or1200_amultp2_32x32 or1200_amultp2_32x32(
	.X(x),
	.Y(y),
	.RST(rst),
	.CLK(clk),
	.P(mul_prod)
);
`else // OR1200_ASIC_MULTP2_32X32
or1200_gmultp2_32x32 or1200_gmultp2_32x32(
	.X(x),
	.Y(y),
	.RST(rst),
	.CLK(clk),
	.P(mul_prod)
);
`endif // OR1200_ASIC_MULTP2_32X32
 
//
// Registered output from the multiplier and
// an optional divider
//
always @(posedge rst or posedge clk)
	if (rst) begin
		mul_prod_r <=  64'h0000_0000_0000_0000;
		div_free <=  1'b1;
`ifdef OR1200_DIV_IMPLEMENTED
		div_cntr <=  6'b00_0000;
`endif
	end
`ifdef OR1200_DIV_IMPLEMENTED
	else if (|div_cntr) begin
		if (div_tmp[31])
			mul_prod_r <=  {mul_prod_r[62:0], 1'b0};
		else
			mul_prod_r <=  {div_tmp[30:0], mul_prod_r[31:0], 1'b1};
		div_cntr <=  div_cntr - 1'b1;
	end
	else if (alu_op_div_divu && div_free) begin
		mul_prod_r <=  {31'b0, x[31:0], 1'b0};
		div_cntr <=  6'b10_0000;
		div_free <=  1'b0;
	end
`endif // OR1200_DIV_IMPLEMENTED
	else if (div_free | !ex_freeze) begin
		mul_prod_r <=  mul_prod[63:0];
		div_free <=  1'b1;
	end
 
`else // OR1200_MULT_IMPLEMENTED
assign result = {width{1'b0}};
assign mul_prod = {2*width{1'b0}};
assign mul_prod_r = {2*width{1'b0}};
`endif // OR1200_MULT_IMPLEMENTED
 
`ifdef OR1200_MAC_IMPLEMENTED
 
//
// Propagation of l.mac opcode
//
always @(posedge clk or posedge rst)
	if (rst)
		mac_op_r1 <=  `OR1200_MACOP_WIDTH'b0;
	else
		mac_op_r1 <=  mac_op;
 
//
// Propagation of l.mac opcode
//
always @(posedge clk or posedge rst)
	if (rst)
		mac_op_r2 <=  `OR1200_MACOP_WIDTH'b0;
	else
		mac_op_r2 <=  mac_op_r1;
 
//
// Propagation of l.mac opcode
//
always @(posedge clk or posedge rst)
	if (rst)
		mac_op_r3 <=  `OR1200_MACOP_WIDTH'b0;
	else
		mac_op_r3 <=  mac_op_r2;
 
//
// Implementation of MAC
//
always @(posedge rst or posedge clk)
	if (rst)
		mac_r <=  64'h0000_0000_0000_0000;
`ifdef OR1200_MAC_SPR_WE
	else if (spr_maclo_we)
		mac_r[31:0] <=  spr_dat_i;
	else if (spr_machi_we)
		mac_r[63:32] <=  spr_dat_i;
`endif
	else if (mac_op_r3 == `OR1200_MACOP_MAC)
		mac_r <=  mac_r + mul_prod_r;
	else if (mac_op_r3 == `OR1200_MACOP_MSB)
		mac_r <=  mac_r - mul_prod_r;
	else if (macrc_op && !ex_freeze)
		mac_r <=  64'h0000_0000_0000_0000;
 
//
// Stall CPU if l.macrc is in ID and MAC still has to process l.mac instructions
// in EX stage (e.g. inside multiplier)
// This stall signal is also used by the divider.
//
always @(posedge rst or posedge clk)
	if (rst)
		mac_stall_r <=  1'b0;
	else
		mac_stall_r <=  (|mac_op | (|mac_op_r1) | (|mac_op_r2)) & (id_macrc_op | mac_stall_r)
`ifdef OR1200_DIV_IMPLEMENTED
				| (|div_cntr)
`endif
				;
`else // OR1200_MAC_IMPLEMENTED
assign mac_stall_r = 1'b0;
assign mac_r = {2*width{1'b0}};
assign mac_op_r1 = `OR1200_MACOP_WIDTH'b0;
assign mac_op_r2 = `OR1200_MACOP_WIDTH'b0;
assign mac_op_r3 = `OR1200_MACOP_WIDTH'b0;
`endif // OR1200_MAC_IMPLEMENTED
 
endmodule