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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:                                                      ////
////   - if biu_cyc/stb are deasserted and wb_ack_i is asserted   ////
////   and this happens even before aborted_r is asssrted,        ////
////   wb_ack_i will be delivered even though transfer is         ////
////   internally considered already aborted. However most        ////
////   wb_ack_i are externally registered and delayed. Normally   ////
////   this shouldn't cause any problems.                         ////
////                                                              ////
////  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_wb_biu.v,v $
// Revision 2.0  2010/06/30 11:00:00  ORSoC
// Major update: 
// Structure reordered and bugs fixed. 
//
// Revision 1.7  2004/04/05 08:29:57  lampret
// Merged branch_qmem into main tree.
//
// Revision 1.6.4.1  2003/07/08 15:36:37  lampret
// Added embedded memory QMEM.
//
// Revision 1.6  2003/04/07 20:57:46  lampret
// Fixed OR1200_CLKDIV_x_SUPPORTED defines. Fixed order of ifdefs.
//
// Revision 1.5  2002/12/08 08:57:56  lampret
// Added optional support for WB B3 specification (xwb_cti_o, xwb_bte_o). Made xwb_cab_o optional.
//
// Revision 1.4  2002/09/16 03:09:16  lampret
// Fixed a combinational loop.
//
// Revision 1.3  2002/08/12 05:31:37  lampret
// Added optional retry counter for wb_rty_i. Added graceful termination for aborted transfers.
//
// Revision 1.2  2002/07/14 22:17:17  lampret
// Added simple trace buffer [only for Xilinx Virtex target]. Fixed instruction fetch abort when new exception is recognized.
//
// Revision 1.1  2002/01/03 08:16:15  lampret
// New prefixes for RTL files, prefixed module names. Updated cache controllers and MMUs.
//
// 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_dat_o,
`ifdef OR1200_WB_CAB
	wb_cab_o,
`endif
`ifdef OR1200_WB_B3
	wb_cti_o, wb_bte_o,
`endif
 
	// 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	[dw-1:0]		wb_dat_o;	// output data bus
`ifdef OR1200_WB_CAB
output				wb_cab_o;	// consecutive address burst
`endif
`ifdef OR1200_WB_B3
output	[2:0]			wb_cti_o;	// cycle type identifier
output	[1:0]			wb_bte_o;	// burst type extension
`endif
 
//
// 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
//
wire				wb_ack;		// normal termination
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
`ifdef OR1200_WB_CAB
reg				wb_cab_o;	// CAB output
`endif
`ifdef OR1200_WB_B3
reg	[2:0]			wb_cti_o;	// cycle type identifier
reg	[1:0]			wb_bte_o;	// burst type extension
`endif
reg	[dw-1:0]		wb_dat_o;	// output data bus
 
`ifdef OR1200_WB_RETRY
reg	[`OR1200_WB_RETRY-1:0]	retry_cnt;	// Retry counter
`else
wire				retry_cnt	= 1'b0;
`endif
`ifdef OR1200_WB_B3
reg	[1:0]			burst_len;	// burst counter
`endif
 
reg  				biu_stb_reg;	// WB strobe
wire  				biu_stb;	// WB strobe
reg				wb_cyc_nxt;	// next WB cycle value
reg				wb_stb_nxt;	// next WB strobe value
reg	[2:0]			wb_cti_nxt;	// next cycle type identifier value
 
reg				wb_ack_cnt;	// WB ack toggle counter
reg				wb_err_cnt;	// WB err toggle counter
reg				wb_rty_cnt;	// WB rty toggle counter
reg				biu_ack_cnt;	// BIU ack toggle counter
reg				biu_err_cnt;	// BIU err toggle counter
reg				biu_rty_cnt;	// BIU rty toggle counter
wire				biu_rty;	// BIU rty indicator
 
reg	[1:0]			wb_fsm_state_cur;	// WB FSM - surrent state
reg	[1:0]			wb_fsm_state_nxt;	// WB FSM - next state
wire	[1:0]			wb_fsm_idle	= 2'h0;	// WB FSM state - IDLE
wire	[1:0]			wb_fsm_trans	= 2'h1;	// WB FSM state - normal TRANSFER
wire	[1:0]			wb_fsm_last	= 2'h2;	// EB FSM state - LAST transfer
 
//
// WISHBONE I/F <-> Internal RISC I/F conversion
//
//assign wb_ack = wb_ack_i;
assign wb_ack = wb_ack_i && !wb_err_i && !wb_rty_i;
 
//
// WB FSM - register part
// 
always @(posedge wb_clk_i or posedge wb_rst_i) begin
	if (wb_rst_i) 
		wb_fsm_state_cur <= #1 wb_fsm_idle;
	else 
		wb_fsm_state_cur <= #1 wb_fsm_state_nxt;
end
 
//
// WB burst tength counter
// 
always @(posedge wb_clk_i or posedge wb_rst_i) begin
	if (wb_rst_i) begin
		burst_len <= #1 2'h0;
	end
	else begin
		// burst counter
		if (wb_fsm_state_cur == wb_fsm_idle)
			burst_len <= #1 2'h2;
		else if (wb_stb_o && wb_ack)
			burst_len <= #1 burst_len - 1'b1;
	end
end
 
// 
// WB FSM - combinatorial part
// 
always @(wb_fsm_state_cur or burst_len or
	 wb_err_i or wb_rty_i or wb_ack or wb_cti_o or wb_sel_o or wb_stb_o or wb_we_o or
	 biu_cyc_i or biu_stb or biu_cab_i or biu_sel_i or biu_we_i) begin
// States of WISHBONE Finite State Machine
	case(wb_fsm_state_cur)
	// IDLE 
	wb_fsm_idle : begin
	    	wb_cyc_nxt = biu_cyc_i && biu_stb;
	    	wb_stb_nxt = biu_cyc_i && biu_stb;
	    	wb_cti_nxt = {!biu_cab_i, 1'b1, !biu_cab_i};
	    	if (biu_cyc_i && biu_stb)
	    		wb_fsm_state_nxt = wb_fsm_trans;
	    	else
	    		wb_fsm_state_nxt = wb_fsm_idle;
	end
	// normal TRANSFER
	wb_fsm_trans : begin
		wb_cyc_nxt = !wb_stb_o || !wb_err_i && !wb_rty_i && !(wb_ack && wb_cti_o == 3'b111);
		wb_stb_nxt = !wb_stb_o || !wb_err_i && !wb_rty_i && !wb_ack || !wb_err_i && !wb_rty_i && wb_cti_o == 3'b010 && !wb_we_o;
		wb_cti_nxt[2] = wb_stb_o && wb_ack && burst_len == 'h0 || wb_cti_o[2];
		wb_cti_nxt[1] = 1'b1  ;
		wb_cti_nxt[0] = wb_stb_o && wb_ack && burst_len == 'h0 || wb_cti_o[0];
		//if ((!biu_cyc_i || !biu_stb || !biu_cab_i) && wb_cti_o == 3'b010  || biu_sel_i != wb_sel_o || biu_we_i != wb_we_o)
		if ((!biu_cyc_i || !biu_stb || !biu_cab_i || biu_sel_i != wb_sel_o || biu_we_i != wb_we_o) && wb_cti_o == 3'b010)
			wb_fsm_state_nxt = wb_fsm_last;
		else if ((wb_err_i || wb_rty_i || wb_ack && wb_cti_o == 3'b111) && wb_stb_o)
			wb_fsm_state_nxt = wb_fsm_idle;
		else
			wb_fsm_state_nxt = wb_fsm_trans;
	end
	// LAST transfer
	wb_fsm_last : begin
		wb_cyc_nxt = !wb_stb_o || !wb_err_i && !wb_rty_i && !(wb_ack && wb_cti_o == 3'b111);
		wb_stb_nxt = !wb_stb_o || !wb_err_i && !wb_rty_i && !(wb_ack && wb_cti_o == 3'b111);
		wb_cti_nxt[2] = wb_ack && wb_stb_o || wb_cti_o[2];
		wb_cti_nxt[1] = 1'b1                  ;
		wb_cti_nxt[0] = wb_ack && wb_stb_o || wb_cti_o[0];
		if ((wb_err_i || wb_rty_i || wb_ack && wb_cti_o == 3'b111) && wb_stb_o)
			wb_fsm_state_nxt = wb_fsm_idle;
		else
			wb_fsm_state_nxt = wb_fsm_last;
	end
	// default state
	default:begin
		wb_cyc_nxt = 1'bx;
		wb_stb_nxt = 1'bx;
		wb_cti_nxt = 3'bxxx;
		wb_fsm_state_nxt = 2'bxx;
	end
	endcase
end
 
//
// WB FSM - output signals
// 
always @(posedge wb_clk_i or posedge wb_rst_i) begin
	if (wb_rst_i) begin
		wb_cyc_o	<= #1 1'b0;
		wb_stb_o	<= #1 1'b0;
		wb_cti_o	<= #1 3'b111;
		wb_bte_o	<= #1 2'b01;	// 4-beat wrap burst = constant
`ifdef OR1200_WB_CAB
		wb_cab_o	<= #1 1'b0;
`endif
		wb_we_o		<= #1 1'b0;
		wb_sel_o	<= #1 4'hf;
		wb_adr_o	<= #1 {aw{1'b0}};
		wb_dat_o	<= #1 {dw{1'b0}};
	end
	else begin
		wb_cyc_o	<= #1 wb_cyc_nxt;
//		wb_stb_o	<= #1 wb_stb_nxt;
                if (wb_ack && wb_cti_o == 3'b111) 
                        wb_stb_o        <= #1 1'b0;
                else
                        wb_stb_o        <= #1 wb_stb_nxt;
		wb_cti_o	<= #1 wb_cti_nxt;
		wb_bte_o	<= #1 2'b01;	// 4-beat wrap burst = constant
`ifdef OR1200_WB_CAB
		wb_cab_o	<= #1 biu_cab_i;
`endif
		// we and sel - set at beginning of access 
		if (wb_fsm_state_cur == wb_fsm_idle) begin
			wb_we_o		<= #1 biu_we_i;
			wb_sel_o	<= #1 biu_sel_i;
		end
		// adr - set at beginning of access and changed at every termination 
		if (wb_fsm_state_cur == wb_fsm_idle) begin
		   wb_adr_o	<= #1 biu_adr_i;
		end 
		else if (wb_stb_o && wb_ack) begin
			wb_adr_o[3:2]	<= #1 wb_adr_o[3:2] + 1'b1;
		end
		// dat - write data changed after avery subsequent write access
		if (!wb_stb_o) begin
			wb_dat_o 	<= #1 biu_dat_i;
		end
	end
end
 
//
// WB & BIU termination toggle counters
// 
always @(posedge wb_clk_i or posedge wb_rst_i) begin
	if (wb_rst_i) begin
		wb_ack_cnt	<= #1 1'b0;
		wb_err_cnt	<= #1 1'b0;
		wb_rty_cnt	<= #1 1'b0;
	end
	else begin
		// WB ack toggle counter
		if (wb_fsm_state_cur == wb_fsm_idle || !clmode)
			wb_ack_cnt	<= #1 1'b0;
		else if (wb_stb_o && wb_ack)
			wb_ack_cnt	<= #1 !wb_ack_cnt;
		// WB err toggle counter
		if (wb_fsm_state_cur == wb_fsm_idle || !clmode)
			wb_err_cnt	<= #1 1'b0;
		else if (wb_stb_o && wb_err_i)
			wb_err_cnt	<= #1 !wb_err_cnt;
		// WB rty toggle counter
		if (wb_fsm_state_cur == wb_fsm_idle || !clmode)
			wb_rty_cnt	<= #1 1'b0;
		else if (wb_stb_o && wb_rty_i)
			wb_rty_cnt	<= #1 !wb_rty_cnt;
	end
end
 
always @(posedge clk or posedge rst) begin
	if (rst) begin
                biu_stb_reg	<= #1 1'b0;
		biu_ack_cnt	<= #1 1'b0;
		biu_err_cnt	<= #1 1'b0;
		biu_rty_cnt	<= #1 1'b0;
`ifdef OR1200_WB_RETRY
		retry_cnt	<= {`OR1200_WB_RETRY{1'b0}};
`endif
	end
	else begin
		// BIU strobe
		if (biu_stb_i && !biu_cab_i && biu_ack_o)
			biu_stb_reg	<= #1 1'b0;
		else
			biu_stb_reg	<= #1 biu_stb_i;
		// BIU ack toggle counter
		if (wb_fsm_state_cur == wb_fsm_idle || !clmode)
			biu_ack_cnt	<= #1 1'b0 ;
		else if (biu_ack_o)
			biu_ack_cnt	<= #1 !biu_ack_cnt ;
		// BIU err toggle counter
		if (wb_fsm_state_cur == wb_fsm_idle || !clmode)
			biu_err_cnt	<= #1 1'b0 ;
		else if (wb_err_i && biu_err_o)
			biu_err_cnt	<= #1 !biu_err_cnt ;
		// BIU rty toggle counter
		if (wb_fsm_state_cur == wb_fsm_idle || !clmode)
			biu_rty_cnt	<= #1 1'b0 ;
		else if (biu_rty)
			biu_rty_cnt	<= #1 !biu_rty_cnt ;
`ifdef OR1200_WB_RETRY
		if (biu_ack_o || biu_err_o)
			retry_cnt	<= #1 {`OR1200_WB_RETRY{1'b0}};
		else if (biu_rty)
			retry_cnt	<= #1 retry_cnt + 1'b1;
`endif
	end
end
 
assign biu_stb = biu_stb_i && biu_stb_reg;
 
//
// Input BIU data bus
//
assign	biu_dat_o	= wb_dat_i;
 
//
// Input BIU termination signals 
//
assign	biu_rty		= (wb_fsm_state_cur == wb_fsm_trans) && wb_rty_i && wb_stb_o && (wb_rty_cnt ~^ biu_rty_cnt);
assign	biu_ack_o	= (wb_fsm_state_cur == wb_fsm_trans) && wb_ack && wb_stb_o && (wb_ack_cnt ~^ biu_ack_cnt);
assign	biu_err_o	= (wb_fsm_state_cur == wb_fsm_trans) && wb_err_i && wb_stb_o && (wb_err_cnt ~^ biu_err_cnt)
`ifdef OR1200_WB_RETRY
			|| biu_rty && retry_cnt[`OR1200_WB_RETRY-1];
`else
			;
`endif
 
 
endmodule