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//////////////////////////////////////////////////////////////////////
////                                                              ////
////  OR1200's register file inside CPU                           ////
////                                                              ////
////  This file is part of the OpenRISC 1200 project              ////
////  http://www.opencores.org/cores/or1k/                        ////
////                                                              ////
////  Description                                                 ////
////  Instantiation of register file memories                     ////
////                                                              ////
////  To Do:                                                      ////
////   - make it smaller and faster                               ////
////                                                              ////
////  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: not supported by cvs2svn $
// Revision 1.3  2001/08/09 13:39:33  lampret
// Major clean-up.
//
// Revision 1.2  2001/07/22 03:31:54  lampret
// Fixed RAM's oen bug. Cache bypass under development.
//
// Revision 1.1  2001/07/20 00:46:21  lampret
// Development version of RTL. Libraries are missing.
//
//
 
// synopsys translate_off
`include "timescale.v"
// synopsys translate_on
`include "defines.v"
 
module rf(
	// Clock and reset
	clk, rst,
 
	// Write i/f
	addrw, dataw, we,
 
	// Read i/f
	id_freeze, addra, addrb, dataa, datab,
 
	// Debug
	spr_cs, spr_write, spr_addr, spr_dat_i, spr_dat_o
);
 
parameter dw = `OPERAND_WIDTH;
parameter aw = `REGFILE_ADDR_WIDTH;
 
//
// I/O
//
 
//
// Clock and reset
//
input				clk;
input				rst;
 
//
// Write i/f
//
input	[aw-1:0]		addrw;
input	[dw-1:0]		dataw;
input				we;
 
//
// Read i/f
//
input				id_freeze;
input	[aw-1:0]		addra;
input	[aw-1:0]		addrb;
output	[dw-1:0]		dataa;
output	[dw-1:0]		datab;
 
//
// SPR access for debugging purposes
//
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
//
wire	[dw-1:0]		from_rfa;
wire	[dw-1:0]		from_rfb;
reg	[dw:0]			dataa_saved;
reg	[dw:0]			datab_saved;
wire	[aw-1:0]		rf_addra;
wire	[aw-1:0]		rf_addrw;
wire	[dw-1:0]		rf_dataw;
wire				rf_we;
wire				spr_valid;
 
//
// SPR access is valid when spr_cs is asserted and
// SPR address matches GPR addresses
//
assign spr_valid = spr_cs & (spr_addr[10:5] == `SPR_RF);
 
//
// SPR data output is always from RF A
//
assign spr_dat_o = from_rfa;
 
//
// Operand A comes from RF or from saved A register
//
assign dataa = (dataa_saved[32]) ? dataa_saved[31:0] : from_rfa;
 
//
// Operand B comes from RF or from saved B register
//
assign datab = (datab_saved[32]) ? datab_saved[31:0] : from_rfb;
 
//
// RF A read address is either from SPRS or normal from CPU control
//
assign rf_addra = (spr_valid & !spr_write) ? spr_addr[4:0] : addra;
 
//
// RF write address is either from SPRS or normal from CPU control
//
assign rf_addrw = (spr_valid & spr_write) ? spr_addr[4:0] : addrw;
 
//
// RF write data is either from SPRS or normal from CPU datapath
//
assign rf_dataw = (spr_valid & spr_write) ? spr_dat_i : dataw;
 
//
// RF write enable is either from SPRS or normal from CPU control
//
assign rf_we = (spr_valid & spr_write) | we;
 
//
// Stores operand from RF_A into temp reg when pipeline is frozen
//
always @(posedge clk or posedge rst)
	if (rst) begin
		dataa_saved <= #1 33'b0;
	end
	else if (id_freeze & !dataa_saved[32]) begin
		dataa_saved <= #1 {1'b1, from_rfa};
	end
	else if (!id_freeze)
		dataa_saved <= #1 33'b0;
 
//
// Stores operand from RF_B into temp reg when pipeline is frozen
//
always @(posedge clk or posedge rst)
	if (rst) begin
		datab_saved <= #1 33'b0;
	end
	else if (id_freeze & !datab_saved[32]) begin
		datab_saved <= #1 {1'b1, from_rfb};
	end
	else if (!id_freeze)
		datab_saved <= #1 33'b0;
 
//
// Instantiation of register file two-port RAM A
//
generic_tpram_32x32 rf_a(
	// Port A
	.clk_a(clk),
	.rst_a(rst),
	.ce_a(1'b1),
	.we_a(1'b0),
	.oe_a(1'b1),
	.addr_a(rf_addra),
	.di_a(32'h0000_0000),
	.do_a(from_rfa),
 
	// Port B
	.clk_b(clk),
	.rst_b(rst),
	.ce_b(rf_we),
	.we_b(rf_we),
	.oe_b(1'b0),
	.addr_b(rf_addrw),
	.di_b(rf_dataw),
	.do_b()
);
 
//
// Instantiation of register file two-port RAM B
//
generic_tpram_32x32 rf_b(
	// Port A
	.clk_a(clk),
	.rst_a(rst),
	.ce_a(1'b1),
	.we_a(1'b0),
	.oe_a(1'b1),
	.addr_a(addrb),
	.di_a(32'h0000_0000),
	.do_a(from_rfb),
 
	// Port B
	.clk_b(clk),
	.rst_b(rst),
	.ce_b(rf_we),
	.we_b(rf_we),
	.oe_b(1'b0),
	.addr_b(rf_addrw),
	.di_b(rf_dataw),
	.do_b()
);
 
endmodule