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//////////////////////////////////////////////////////////////////////
////                                                              ////
////  OR1200's WISHBONE BIU                                       ////
////                                                              ////
////  This file is part of the OpenRISC 1200 project              ////
////  http://www.opencores.org/cores/or1k/                        ////
////                                                              ////
////  Description                                                 ////
////  Implements WISHBONE interface                               ////
////                                                              ////
////  To Do:                                                      ////
////   - add support for wb_err_i                                 ////
////                                                              ////
////  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 1.12  2001/11/22 13:42:51  lampret
// Added wb_cyc_o assignment after it was removed by accident.
//
// Revision 1.11  2001/11/20 21:28:10  lampret
// Added optional sampling of inputs.
//
// Revision 1.10  2001/11/18 11:32:00  lampret
// OR1200_REGISTERED_OUTPUTS can now be enabled.
//
// Revision 1.9  2001/10/21 17:57:16  lampret
// Removed params from generic_XX.v. Added translate_off/on in sprs.v and id.v. Removed spr_addr from dc.v and ic.v. Fixed CR+LF.
//
// Revision 1.8  2001/10/14 13:12:10  lampret
// MP3 version.
//
// Revision 1.1.1.1  2001/10/06 10:18:35  igorm
// no message
//
// 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 00:46:23  lampret
// Development version of RTL. Libraries are missing.
//
//
 
// synopsys translate_off
`include "timescale.v"
// synopsys translate_on
`include "or1200_defines.v"
 
module or1200_wb_biu(
	// RISC clock, reset and clock control
	clk, rst, clmode,
 
	// WISHBONE interface
	wb_clk_i, wb_rst_i, wb_ack_i, wb_err_i, wb_rty_i, wb_dat_i,
	wb_cyc_o, wb_adr_o, wb_stb_o, wb_we_o, wb_sel_o, wb_cab_o, wb_dat_o,
 
	// Internal RISC bus
	biu_dat_i, biu_adr_i, biu_cyc_i, biu_stb_i, biu_we_i, biu_sel_i, biu_cab_i,
	biu_dat_o, biu_ack_o, biu_err_o
);
 
parameter dw = `OR1200_OPERAND_WIDTH;
parameter aw = `OR1200_OPERAND_WIDTH;
 
//
// RISC clock, reset and clock control
//
input			clk;		// RISC clock
input			rst;		// RISC reset
input	[1:0]		clmode;		// 00 WB=RISC, 01 WB=RISC/2, 10 N/A, 11 WB=RISC/4
 
//
// WISHBONE interface
//
input			wb_clk_i;	// clock input
input			wb_rst_i;	// reset input
input			wb_ack_i;	// normal termination
input			wb_err_i;	// termination w/ error
input			wb_rty_i;	// termination w/ retry
input	[dw-1:0]	wb_dat_i;	// input data bus
output			wb_cyc_o;	// cycle valid output
output	[aw-1:0]	wb_adr_o;	// address bus outputs
output			wb_stb_o;	// strobe output
output			wb_we_o;	// indicates write transfer
output	[3:0]		wb_sel_o;	// byte select outputs
output			wb_cab_o;	// consecutive address burst
output	[dw-1:0]	wb_dat_o;	// output data bus
 
//
// Internal RISC interface
//
input	[dw-1:0]	biu_dat_i;	// input data bus
input	[aw-1:0]	biu_adr_i;	// address bus
input			biu_cyc_i;	// WB cycle
input			biu_stb_i;	// WB strobe
input			biu_we_i;	// WB write enable
input			biu_cab_i;	// CAB input
input	[3:0]		biu_sel_i;	// byte selects
output	[31:0]		biu_dat_o;	// output data bus
output			biu_ack_o;	// ack output
output			biu_err_o;	// err output
 
//
// Registers
//
reg	[1:0]		valid_div;	// Used for synchronization
`ifdef OR1200_REGISTERED_OUTPUTS
reg	[aw-1:0]	wb_adr_o;	// address bus outputs
reg			wb_cyc_o;	// cycle output
reg			wb_stb_o;	// strobe output
reg			wb_we_o;	// indicates write transfer
reg	[3:0]		wb_sel_o;	// byte select outputs
reg			wb_cab_o;	// CAB output
reg	[dw-1:0]	wb_dat_o;	// output data bus
`endif
`ifdef OR1200_REGISTERED_INPUTS
reg			long_ack_o;	// normal termination
reg			long_err_o;	// error termination
reg	[dw-1:0]	biu_dat_o;	// output data bus
`else
wire			long_ack_o;	// normal termination
wire			long_err_o;	// error termination
`endif
 
//
// WISHBONE I/F <-> Internal RISC I/F conversion
//
 
//
// Address bus
//
`ifdef OR1200_REGISTERED_OUTPUTS
always @(posedge wb_clk_i or posedge wb_rst_i)
	if (wb_rst_i)
		wb_adr_o <= #1 {aw{1'b0}};
	else if ((biu_cyc_i & biu_stb_i) & ~wb_ack_i)
		wb_adr_o <= #1 biu_adr_i;
`else
assign wb_adr_o = biu_adr_i;
`endif
 
//
// Input data bus
//
`ifdef OR1200_REGISTERED_INPUTS
always @(posedge wb_clk_i or posedge wb_rst_i)
	if (wb_rst_i)
		biu_dat_o <= #1 32'h0000_0000;
	else if (wb_ack_i)
		biu_dat_o <= #1 wb_dat_i;
`else
assign biu_dat_o = wb_dat_i;
`endif
 
//
// Output data bus
//
`ifdef OR1200_REGISTERED_OUTPUTS
always @(posedge wb_clk_i or posedge wb_rst_i)
	if (wb_rst_i)
		wb_dat_o <= #1 {dw{1'b0}};
	else if ((biu_cyc_i & biu_stb_i) & ~wb_ack_i)
		wb_dat_o <= #1 biu_dat_i;
`else
assign wb_dat_o = biu_dat_i;
`endif
 
//
// Valid_div counts RISC clock cycles by modulo 4
// and is used to synchronize external WB i/f to
// RISC clock
//
always @(posedge clk or posedge rst)
	if (rst)
		valid_div <= #1 2'b0;
	else
		valid_div <= #1 valid_div + 'd1;
 
//
// biu_ack_o is one RISC clock cycle long long_ack_o.
// long_ack_o is one, two or four RISC clock cycles long because
// WISHBONE can work at 1, 1/2 or 1/4 RISC clock.
//
assign biu_ack_o = long_ack_o
`ifdef OR1200_CLKDIV_4_SUPPORTED
		& (valid_div[1] | ~clmode[1])
`ifdef OR1200_CLKDIV_2_SUPPORTED
		& (valid_div[0] | ~clmode[0])
`endif
`endif
		;
 
//
// Acknowledgment of the data to the RISC
//
// long_ack_o
//
`ifdef OR1200_REGISTERED_INPUTS
always @(posedge wb_clk_i or posedge wb_rst_i)
	if (wb_rst_i)
		long_ack_o <= #1 1'b0;
	else
		long_ack_o <= #1 wb_ack_i;
`else
assign long_ack_o = wb_ack_i;
`endif
 
//
// biu_err_o is one RISC clock cycle long long_err_o.
// long_err_o is one, two or four RISC clock cycles long because
// WISHBONE can work at 1, 1/2 or 1/4 RISC clock.
//
assign biu_err_o = long_err_o
`ifdef OR1200_CLKDIV_4_SUPPORTED
		& (valid_div[1] | ~clmode[1])
`ifdef OR1200_CLKDIV_2_SUPPORTED
		& (valid_div[0] | ~clmode[0])
`endif
`endif
		;
 
//
// Error termination
//
// long_err_o
//
`ifdef OR1200_REGISTERED_INPUTS
always @(posedge wb_clk_i or posedge wb_rst_i)
	if (wb_rst_i)
		long_err_o <= #1 1'b0;
	else
		long_err_o <= #1 wb_err_i;
`else
assign long_err_o = wb_err_i;
`endif
 
//
// WB cyc_o
//
`ifdef OR1200_REGISTERED_OUTPUTS
always @(posedge wb_clk_i or posedge wb_rst_i)
	if (wb_rst_i)
		wb_cyc_o <= #1 1'b0;
	else
		wb_cyc_o <= #1 biu_cyc_i & ~wb_ack_i | biu_cab_i;
`else
assign wb_cyc_o = biu_cyc_i | biu_cab_i;
`endif
 
//
// WB stb_o
//
`ifdef OR1200_REGISTERED_OUTPUTS
always @(posedge wb_clk_i or posedge wb_rst_i)
	if (wb_rst_i)
		wb_stb_o <= #1 1'b0;
	else
		wb_stb_o <= #1 (biu_cyc_i & biu_stb_i) & ~wb_ack_i;
`else
assign wb_stb_o = biu_cyc_i & biu_stb_i;
`endif
 
//
// WB we_o
//
`ifdef OR1200_REGISTERED_OUTPUTS
always @(posedge wb_clk_i or posedge wb_rst_i)
	if (wb_rst_i)
		wb_we_o <= #1 1'b0;
	else
		wb_we_o <= #1 biu_cyc_i & biu_stb_i & biu_we_i;
`else
assign wb_we_o = biu_cyc_i & biu_stb_i & biu_we_i;
`endif
 
//
// WB sel_o
//
`ifdef OR1200_REGISTERED_OUTPUTS
always @(posedge wb_clk_i or posedge wb_rst_i)
	if (wb_rst_i)
		wb_sel_o <= #1 4'b0000;
	else
		wb_sel_o <= #1 biu_sel_i;
`else
assign wb_sel_o = biu_sel_i;
`endif
 
//
// WB cab_o
//
`ifdef OR1200_REGISTERED_OUTPUTS
always @(posedge wb_clk_i or posedge wb_rst_i)
	if (wb_rst_i)
		wb_cab_o <= #1 1'b0;
	else
		wb_cab_o <= #1 biu_cab_i;
`else
assign wb_cab_o = biu_cab_i;
`endif
 
endmodule