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//////////////////////////////////////////////////////////////////////
////                                                              ////
////  OR1200's Instruction decode                                 ////
////                                                              ////
////  This file is part of the OpenRISC 1200 project              ////
////  http://www.opencores.org/project,or1k                       ////
////                                                              ////
////  Description                                                 ////
////  Majority of instruction decoding is performed here.         ////
////                                                              ////
////  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                     ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
//
//
// $Log: or1200_ctrl.v,v $
// Revision 2.0  2010/06/30 11:00:00  ORSoC
// Major update: 
// Structure reordered and bugs fixed. 
 
// synopsys translate_off
`include "timescale.v"
// synopsys translate_on
`include "or1200_defines.v"
 
module or1200_ctrl
  (
   // Clock and reset
   clk, rst,
 
   // Internal i/f
   except_flushpipe, extend_flush, if_flushpipe, id_flushpipe, ex_flushpipe, 
   wb_flushpipe,
   id_freeze, ex_freeze, wb_freeze, if_insn, id_insn, ex_insn, abort_mvspr, 
   id_branch_op, ex_branch_op, ex_branch_taken, pc_we, 
   rf_addra, rf_addrb, rf_rda, rf_rdb, alu_op, alu_op2, mac_op,
   comp_op, rf_addrw, rfwb_op, fpu_op,
   wb_insn, id_simm, ex_simm, id_branch_addrtarget, ex_branch_addrtarget, sel_a,
   sel_b, id_lsu_op,
   cust5_op, cust5_limm, id_pc, ex_pc, du_hwbkpt, 
   multicycle, wait_on, wbforw_valid, sig_syscall, sig_trap,
   force_dslot_fetch, no_more_dslot, id_void, ex_void, ex_spr_read, 
   ex_spr_write, 
   id_mac_op, id_macrc_op, ex_macrc_op, rfe, except_illegal, dc_no_writethrough
   );
 
//
// I/O
//
input					clk;
input					rst;
input					id_freeze;
input					ex_freeze /* verilator public */;
input					wb_freeze /* verilator public */;
output					if_flushpipe;
output					id_flushpipe;
output					ex_flushpipe;
output					wb_flushpipe;
input					extend_flush;
input					except_flushpipe;
input                           abort_mvspr ;
input	[31:0]			if_insn;
output	[31:0]			id_insn;
output	[31:0]			ex_insn /* verilator public */;
output	[`OR1200_BRANCHOP_WIDTH-1:0]		ex_branch_op;
output	[`OR1200_BRANCHOP_WIDTH-1:0]		id_branch_op;
input						ex_branch_taken;
output	[`OR1200_REGFILE_ADDR_WIDTH-1:0]	rf_addrw;
output	[`OR1200_REGFILE_ADDR_WIDTH-1:0]	rf_addra;
output	[`OR1200_REGFILE_ADDR_WIDTH-1:0]	rf_addrb;
output					rf_rda;
output					rf_rdb;
output	[`OR1200_ALUOP_WIDTH-1:0]		alu_op;
output [`OR1200_ALUOP2_WIDTH-1:0] 		alu_op2;
output	[`OR1200_MACOP_WIDTH-1:0]		mac_op;
output	[`OR1200_RFWBOP_WIDTH-1:0]		rfwb_op;
output  [`OR1200_FPUOP_WIDTH-1:0] 		fpu_op;      
input					pc_we;
output	[31:0]				wb_insn;
output	[31:2]				id_branch_addrtarget;
output	[31:2]				ex_branch_addrtarget;
output	[`OR1200_SEL_WIDTH-1:0]		sel_a;
output	[`OR1200_SEL_WIDTH-1:0]		sel_b;
output	[`OR1200_LSUOP_WIDTH-1:0]		id_lsu_op;
output	[`OR1200_COMPOP_WIDTH-1:0]		comp_op;
output	[`OR1200_MULTICYCLE_WIDTH-1:0]		multicycle;
output  [`OR1200_WAIT_ON_WIDTH-1:0] 		wait_on;   
output	[4:0]				cust5_op;
output	[5:0]				cust5_limm;
input   [31:0]                          id_pc;
input   [31:0]                          ex_pc;
output	[31:0]				id_simm;
output	[31:0]				ex_simm;
input					wbforw_valid;
input					du_hwbkpt;
output					sig_syscall;
output					sig_trap;
output					force_dslot_fetch;
output					no_more_dslot;
output					id_void;
output					ex_void;
output					ex_spr_read;
output					ex_spr_write;
output	[`OR1200_MACOP_WIDTH-1:0]	id_mac_op;
output					id_macrc_op;
output					ex_macrc_op;
output					rfe;
output					except_illegal;
output  				dc_no_writethrough;
 
 
//
// Internal wires and regs
//
reg	[`OR1200_BRANCHOP_WIDTH-1:0]		id_branch_op;
reg	[`OR1200_BRANCHOP_WIDTH-1:0]		ex_branch_op;
reg	[`OR1200_ALUOP_WIDTH-1:0]		alu_op;
reg [`OR1200_ALUOP2_WIDTH-1:0]      		alu_op2;
wire					if_maci_op;
`ifdef OR1200_MAC_IMPLEMENTED
reg	[`OR1200_MACOP_WIDTH-1:0]		ex_mac_op;
reg	[`OR1200_MACOP_WIDTH-1:0]		id_mac_op;
wire	[`OR1200_MACOP_WIDTH-1:0]		mac_op;
reg					ex_macrc_op;
`else
wire	[`OR1200_MACOP_WIDTH-1:0]		mac_op;
wire					ex_macrc_op;
`endif
reg	[31:0]				id_insn /* verilator public */;
reg	[31:0]				ex_insn /* verilator public */;
reg	[31:0]				wb_insn /* verilator public */;
reg	[`OR1200_REGFILE_ADDR_WIDTH-1:0]	rf_addrw;
reg	[`OR1200_REGFILE_ADDR_WIDTH-1:0]	wb_rfaddrw;
reg	[`OR1200_RFWBOP_WIDTH-1:0]		rfwb_op;
reg	[`OR1200_SEL_WIDTH-1:0]		sel_a;
reg	[`OR1200_SEL_WIDTH-1:0]		sel_b;
reg					sel_imm;
reg	[`OR1200_LSUOP_WIDTH-1:0]		id_lsu_op;
reg	[`OR1200_COMPOP_WIDTH-1:0]		comp_op;
reg	[`OR1200_MULTICYCLE_WIDTH-1:0]		multicycle;
reg     [`OR1200_WAIT_ON_WIDTH-1:0] 		wait_on;      
reg 	[31:0]				id_simm;
reg 	[31:0]				ex_simm;
reg					sig_syscall;
reg					sig_trap;
reg					except_illegal;
wire					id_void;
wire					ex_void;
wire                                    wb_void;
reg                                     ex_delayslot_dsi;
reg                                     ex_delayslot_nop;
reg					spr_read;
reg					spr_write;
reg     [31:2]				ex_branch_addrtarget;
`ifdef OR1200_DC_NOSTACKWRITETHROUGH
reg 					dc_no_writethrough;
`endif
 
//
// Register file read addresses
//
assign rf_addra = if_insn[20:16];
assign rf_addrb = if_insn[15:11];
assign rf_rda = if_insn[31] || if_maci_op;
assign rf_rdb = if_insn[30];
 
//
// Force fetch of delay slot instruction when jump/branch is preceeded by 
// load/store instructions
//
assign force_dslot_fetch = 1'b0;
assign no_more_dslot = (|ex_branch_op & !id_void & ex_branch_taken) | 
		       (ex_branch_op == `OR1200_BRANCHOP_RFE);
 
assign id_void = (id_insn[31:26] == `OR1200_OR32_NOP) & id_insn[16];
assign ex_void = (ex_insn[31:26] == `OR1200_OR32_NOP) & ex_insn[16];
assign wb_void = (wb_insn[31:26] == `OR1200_OR32_NOP) & wb_insn[16];
 
assign ex_spr_write = spr_write && !abort_mvspr;
assign ex_spr_read = spr_read && !abort_mvspr;
 
//
// ex_delayslot_dsi: delay slot insn is in EX stage
// ex_delayslot_nop: (filler) nop insn is in EX stage (before nops 
//                   jump/branch was executed)
//
//  ex_delayslot_dsi & !ex_delayslot_nop - DS insn in EX stage
//  !ex_delayslot_dsi & ex_delayslot_nop - NOP insn in EX stage, 
//       next different is DS insn, previous different was Jump/Branch
//  !ex_delayslot_dsi & !ex_delayslot_nop - normal insn in EX stage
//
always @(posedge clk or `OR1200_RST_EVENT rst) begin
        if (rst == `OR1200_RST_VALUE) begin
		ex_delayslot_nop <=  1'b0;
		ex_delayslot_dsi <=  1'b0;
	end
	else if (!ex_freeze & !ex_delayslot_dsi & ex_delayslot_nop) begin
		ex_delayslot_nop <=  id_void;
		ex_delayslot_dsi <=  !id_void;
	end
	else if (!ex_freeze & ex_delayslot_dsi & !ex_delayslot_nop) begin
		ex_delayslot_nop <=  1'b0;
		ex_delayslot_dsi <=  1'b0;
	end
	else if (!ex_freeze) begin
		ex_delayslot_nop <=  id_void && ex_branch_taken && 
				     (ex_branch_op != `OR1200_BRANCHOP_NOP) && 
				     (ex_branch_op != `OR1200_BRANCHOP_RFE);
	        ex_delayslot_dsi <=  !id_void && ex_branch_taken && 
				     (ex_branch_op != `OR1200_BRANCHOP_NOP) && 
				     (ex_branch_op != `OR1200_BRANCHOP_RFE);
	end
end
 
//
// Flush pipeline
//
assign if_flushpipe = except_flushpipe | pc_we | extend_flush;
assign id_flushpipe = except_flushpipe | pc_we | extend_flush;
assign ex_flushpipe = except_flushpipe | pc_we | extend_flush;
assign wb_flushpipe = except_flushpipe | pc_we | extend_flush;
 
//
// EX Sign/Zero extension of immediates
//
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE)
		ex_simm <=  32'h0000_0000;
	else if (!ex_freeze) begin
		ex_simm <=  id_simm;
	end
end
 
//
// ID Sign/Zero extension of immediate
//
always @(id_insn) begin
	case (id_insn[31:26])     // synopsys parallel_case
 
	// l.addi
	`OR1200_OR32_ADDI:
		id_simm = {{16{id_insn[15]}}, id_insn[15:0]};
 
	// l.addic
	`OR1200_OR32_ADDIC:
		id_simm = {{16{id_insn[15]}}, id_insn[15:0]};
 
	// l.lxx (load instructions)
	`OR1200_OR32_LWZ, `OR1200_OR32_LBZ, `OR1200_OR32_LBS, 
	`OR1200_OR32_LHZ, `OR1200_OR32_LHS:
		id_simm = {{16{id_insn[15]}}, id_insn[15:0]};
 
	// l.muli
	`ifdef OR1200_MULT_IMPLEMENTED
	`OR1200_OR32_MULI:
		id_simm = {{16{id_insn[15]}}, id_insn[15:0]};
	`endif
 
	// l.maci
	`ifdef OR1200_MAC_IMPLEMENTED
	`OR1200_OR32_MACI:
		id_simm = {{16{id_insn[15]}}, id_insn[15:0]};
	`endif
 
	// l.mtspr
	`OR1200_OR32_MTSPR:
		id_simm = {16'b0, id_insn[25:21], id_insn[10:0]};
 
	// l.sxx (store instructions)
	`OR1200_OR32_SW, `OR1200_OR32_SH, `OR1200_OR32_SB:
		id_simm = {{16{id_insn[25]}}, id_insn[25:21], id_insn[10:0]};
 
	// l.xori
	`OR1200_OR32_XORI:
		id_simm = {{16{id_insn[15]}}, id_insn[15:0]};
 
	// l.sfxxi (SFXX with immediate)
	`OR1200_OR32_SFXXI:
		id_simm = {{16{id_insn[15]}}, id_insn[15:0]};
 
	// Instructions with no or zero extended immediate
	default:
		id_simm = {{16'b0}, id_insn[15:0]};
 
	endcase
end
 
//
// ID Sign extension of branch offset
//
assign id_branch_addrtarget = {{4{id_insn[25]}}, id_insn[25:0]} + id_pc[31:2];
 
//
// EX Sign extension of branch offset
//
 
// pipeline ID and EX branch target address 
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE)
		ex_branch_addrtarget <=  0;
	else if (!ex_freeze) 
		ex_branch_addrtarget <=  id_branch_addrtarget;
end
// not pipelined
//assign ex_branch_addrtarget = {{4{ex_insn[25]}}, ex_insn[25:0]} + ex_pc[31:2];
 
//
// l.maci in IF stage
//
`ifdef OR1200_MAC_IMPLEMENTED
assign if_maci_op = (if_insn[31:26] == `OR1200_OR32_MACI);
`else
assign if_maci_op = 1'b0;
`endif
 
//
// l.macrc in ID stage
//
`ifdef OR1200_MAC_IMPLEMENTED
assign id_macrc_op = (id_insn[31:26] == `OR1200_OR32_MACRC) & id_insn[16];
`else
assign id_macrc_op = 1'b0;
`endif
 
//
// l.macrc in EX stage
//
`ifdef OR1200_MAC_IMPLEMENTED
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE)
		ex_macrc_op <=  1'b0;
	else if (!ex_freeze & id_freeze | ex_flushpipe)
		ex_macrc_op <=  1'b0;
	else if (!ex_freeze)
		ex_macrc_op <=  id_macrc_op;
end
`else
assign ex_macrc_op = 1'b0;
`endif
 
//
// cust5_op, cust5_limm (L immediate)
//
assign cust5_op = ex_insn[4:0];
assign cust5_limm = ex_insn[10:5];
 
//
//
//
assign rfe = (id_branch_op == `OR1200_BRANCHOP_RFE) | 
	     (ex_branch_op == `OR1200_BRANCHOP_RFE);
 
 
`ifdef verilator
   // Function to access wb_insn (for Verilator). Have to hide this from
   // simulator, since functions with no inputs are not allowed in IEEE
   // 1364-2001.
   function [31:0] get_wb_insn;
      // verilator public
      get_wb_insn = wb_insn;
   endfunction // get_wb_insn
 
   // Function to access id_insn (for Verilator). Have to hide this from
   // simulator, since functions with no inputs are not allowed in IEEE
   // 1364-2001.
   function [31:0] get_id_insn;
      // verilator public
      get_id_insn = id_insn;
   endfunction // get_id_insn
 
   // Function to access ex_insn (for Verilator). Have to hide this from
   // simulator, since functions with no inputs are not allowed in IEEE
   // 1364-2001.
   function [31:0] get_ex_insn;
      // verilator public
      get_ex_insn = ex_insn;
   endfunction // get_ex_insn
 
`endif
 
 
//
// Generation of sel_a
//
always @(rf_addrw or id_insn or rfwb_op or wbforw_valid or wb_rfaddrw)
	if ((id_insn[20:16] == rf_addrw) && rfwb_op[0])
		sel_a = `OR1200_SEL_EX_FORW;
	else if ((id_insn[20:16] == wb_rfaddrw) && wbforw_valid)
		sel_a = `OR1200_SEL_WB_FORW;
	else
		sel_a = `OR1200_SEL_RF;
 
//
// Generation of sel_b
//
always @(rf_addrw or sel_imm or id_insn or rfwb_op or wbforw_valid or 
	 wb_rfaddrw)
	if (sel_imm)
		sel_b = `OR1200_SEL_IMM;
	else if ((id_insn[15:11] == rf_addrw) && rfwb_op[0])
		sel_b = `OR1200_SEL_EX_FORW;
	else if ((id_insn[15:11] == wb_rfaddrw) && wbforw_valid)
		sel_b = `OR1200_SEL_WB_FORW;
	else
		sel_b = `OR1200_SEL_RF;
 
//
// Decode of multicycle
//
always @(id_insn) begin
  case (id_insn[31:26])		// synopsys parallel_case
    // l.mfspr
    `OR1200_OR32_MFSPR:
      multicycle = `OR1200_TWO_CYCLES;	// to read from ITLB/DTLB (sync RAMs)
    // Single cycle instructions
    default: begin
      multicycle = `OR1200_ONE_CYCLE;
    end    
  endcase
end // always @ (id_insn)
 
//
// Encode wait_on signal
//    
always @(id_insn) begin
   case (id_insn[31:26])		// synopsys parallel_case
     `OR1200_OR32_ALU: 
       wait_on =  ( 1'b0
`ifdef OR1200_DIV_IMPLEMENTED
                     | (id_insn[4:0] == `OR1200_ALUOP_DIV)
		     | (id_insn[4:0] == `OR1200_ALUOP_DIVU)
`endif
`ifdef OR1200_MULT_IMPLEMENTED
		     | (id_insn[4:0] == `OR1200_ALUOP_MUL)
		     | (id_insn[4:0] == `OR1200_ALUOP_MULU)
`endif
		    ) ? `OR1200_WAIT_ON_MULTMAC : `OR1200_WAIT_ON_NOTHING;
`ifdef OR1200_MULT_IMPLEMENTED
`ifdef OR1200_MAC_IMPLEMENTED
     `OR1200_OR32_MACMSB,
     `OR1200_OR32_MACI,
`endif
     `OR1200_OR32_MULI:       
	 wait_on = `OR1200_WAIT_ON_MULTMAC;
`endif
`ifdef OR1200_MAC_IMPLEMENTED
     `OR1200_OR32_MACRC:
         wait_on = id_insn[16] ? `OR1200_WAIT_ON_MULTMAC : 
		                 `OR1200_WAIT_ON_NOTHING;
`endif		   
`ifdef OR1200_FPU_IMPLEMENTED
       `OR1200_OR32_FLOAT: begin
	 wait_on = id_insn[`OR1200_FPUOP_DOUBLE_BIT] ? 0 : `OR1200_WAIT_ON_FPU;
       end
`endif
`ifndef OR1200_DC_WRITEHROUGH
     // l.mtspr
     `OR1200_OR32_MTSPR: begin
	wait_on = `OR1200_WAIT_ON_MTSPR;
     end
`endif
     default: begin
	wait_on = `OR1200_WAIT_ON_NOTHING;
     end
   endcase // case (id_insn[31:26])
end // always @ (id_insn)
 
 
 
 
//
// Register file write address
//
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE)
		rf_addrw <=  5'd0;
	else if (!ex_freeze & id_freeze)
		rf_addrw <=  5'd00;
	else if (!ex_freeze)
		case (id_insn[31:26])	// synopsys parallel_case
			`OR1200_OR32_JAL, `OR1200_OR32_JALR:
				rf_addrw <=  5'd09;	// link register r9
			default:
				rf_addrw <=  id_insn[25:21];
		endcase
end
 
//
// rf_addrw in wb stage (used in forwarding logic)
//
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE)
		wb_rfaddrw <=  5'd0;
	else if (!wb_freeze)
		wb_rfaddrw <=  rf_addrw;
end
 
//
// Instruction latch in id_insn
//
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE)
		id_insn <=  {`OR1200_OR32_NOP, 26'h041_0000};
        else if (id_flushpipe)
                id_insn <=  {`OR1200_OR32_NOP, 26'h041_0000};        // NOP -> id_insn[16] must be 1
	else if (!id_freeze) begin
		id_insn <=  if_insn;
`ifdef OR1200_VERBOSE
// synopsys translate_off
		$display("%t: id_insn <= %h", $time, if_insn);
// synopsys translate_on
`endif
	end
end
 
//
// Instruction latch in ex_insn
//
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE)
		ex_insn <=  {`OR1200_OR32_NOP, 26'h041_0000};
	else if (!ex_freeze & id_freeze | ex_flushpipe)
		ex_insn <=  {`OR1200_OR32_NOP, 26'h041_0000};	// NOP -> ex_insn[16] must be 1
	else if (!ex_freeze) begin
		ex_insn <=  id_insn;
`ifdef OR1200_VERBOSE
// synopsys translate_off
		$display("%t: ex_insn <= %h", $time, id_insn);
// synopsys translate_on
`endif
	end
end
 
//
// Instruction latch in wb_insn
//
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE)
		wb_insn <=  {`OR1200_OR32_NOP, 26'h041_0000};
	// wb_insn should not be changed by exceptions due to correct 
	// recording of display_arch_state in the or1200_monitor! 
	// wb_insn changed by exception is not used elsewhere! 
	else if (!wb_freeze) begin
		wb_insn <=  ex_insn;
	end
end
 
//
// Decode of sel_imm
//
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE)
		sel_imm <=  1'b0;
	else if (!id_freeze) begin
	  case (if_insn[31:26])		// synopsys parallel_case
 
	    // j.jalr
	    `OR1200_OR32_JALR:
	      sel_imm <=  1'b0;
 
	    // l.jr
	    `OR1200_OR32_JR:
	      sel_imm <=  1'b0;
 
	    // l.rfe
	    `OR1200_OR32_RFE:
	      sel_imm <=  1'b0;
 
	    // l.mfspr
	    `OR1200_OR32_MFSPR:
	      sel_imm <=  1'b0;
 
	    // l.mtspr
	    `OR1200_OR32_MTSPR:
	      sel_imm <=  1'b0;
 
	    // l.sys, l.brk and all three sync insns
	    `OR1200_OR32_XSYNC:
	      sel_imm <=  1'b0;
 
	    // l.mac/l.msb
`ifdef OR1200_MAC_IMPLEMENTED
	    `OR1200_OR32_MACMSB:
	      sel_imm <=  1'b0;
`endif
 
	    // l.sw
	    `OR1200_OR32_SW:
	      sel_imm <=  1'b0;
 
	    // l.sb
	    `OR1200_OR32_SB:
	      sel_imm <=  1'b0;
 
	    // l.sh
	    `OR1200_OR32_SH:
	      sel_imm <=  1'b0;
 
	    // ALU instructions except the one with immediate
	    `OR1200_OR32_ALU:
	      sel_imm <=  1'b0;
 
	    // SFXX instructions
	    `OR1200_OR32_SFXX:
	      sel_imm <=  1'b0;
 
`ifdef OR1200_IMPL_ALU_CUST5
	    // l.cust5 instructions
	    `OR1200_OR32_CUST5:
	      sel_imm <=  1'b0;
`endif
`ifdef OR1200_FPU_IMPLEMENTED
	    // FPU instructions
	    `OR1200_OR32_FLOAT:
	      sel_imm <=  1'b0;
`endif
	    // l.nop
	    `OR1200_OR32_NOP:
	      sel_imm <=  1'b0;
 
	    // All instructions with immediates
	    default: begin
	      sel_imm <=  1'b1;
	    end
 
	  endcase
 
	end
end
 
//
// Decode of except_illegal
//
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE)
		except_illegal <=  1'b0;
	else if (!ex_freeze & id_freeze | ex_flushpipe)
		except_illegal <=  1'b0;
	else if (!ex_freeze) begin
		case (id_insn[31:26])		// synopsys parallel_case
 
		`OR1200_OR32_J,
		`OR1200_OR32_JAL,
		`OR1200_OR32_JALR,
		`OR1200_OR32_JR,
		`OR1200_OR32_BNF,
		`OR1200_OR32_BF,
		`OR1200_OR32_RFE,
		`OR1200_OR32_MOVHI,
		`OR1200_OR32_MFSPR,
		`OR1200_OR32_XSYNC,
`ifdef OR1200_MAC_IMPLEMENTED
		`OR1200_OR32_MACI,
`endif
		`OR1200_OR32_LWZ,
		`OR1200_OR32_LBZ,
		`OR1200_OR32_LBS,
		`OR1200_OR32_LHZ,
		`OR1200_OR32_LHS,
		`OR1200_OR32_ADDI,
		`OR1200_OR32_ADDIC,
		`OR1200_OR32_ANDI,
		`OR1200_OR32_ORI,
		`OR1200_OR32_XORI,
`ifdef OR1200_MULT_IMPLEMENTED
		`OR1200_OR32_MULI,
`endif
		`OR1200_OR32_SH_ROTI,
		`OR1200_OR32_SFXXI,
		`OR1200_OR32_MTSPR,
`ifdef OR1200_MAC_IMPLEMENTED
		`OR1200_OR32_MACMSB,
`endif
		`OR1200_OR32_SW,
		`OR1200_OR32_SB,
		`OR1200_OR32_SH,
		`OR1200_OR32_SFXX,
`ifdef OR1200_IMPL_ALU_CUST5
		`OR1200_OR32_CUST5,
`endif
	`OR1200_OR32_NOP:
		except_illegal <=  1'b0;
`ifdef OR1200_FPU_IMPLEMENTED
	    `OR1200_OR32_FLOAT:
                // Check it's not a double precision instruction
                except_illegal <=  id_insn[`OR1200_FPUOP_DOUBLE_BIT];
`endif	      
 
	`OR1200_OR32_ALU:
		except_illegal <=  1'b0 
 
`ifdef OR1200_MULT_IMPLEMENTED
`ifdef OR1200_DIV_IMPLEMENTED
`else 
		| (id_insn[4:0] == `OR1200_ALUOP_DIV)
		| (id_insn[4:0] == `OR1200_ALUOP_DIVU)
`endif
`else
		| (id_insn[4:0] == `OR1200_ALUOP_DIV)
		| (id_insn[4:0] == `OR1200_ALUOP_DIVU)
		| (id_insn[4:0] == `OR1200_ALUOP_MUL)
`endif
 
`ifdef OR1200_IMPL_ADDC
`else
		| (id_insn[4:0] == `OR1200_ALUOP_ADDC)
`endif
 
`ifdef OR1200_IMPL_ALU_FFL1
`else
		| (id_insn[4:0] == `OR1200_ALUOP_FFL1)
`endif
 
`ifdef OR1200_IMPL_ALU_ROTATE
`else
		| ((id_insn[4:0] == `OR1200_ALUOP_SHROT) &
		   (id_insn[9:6] == `OR1200_SHROTOP_ROR))
`endif
 
`ifdef OR1200_IMPL_SUB
`else
		| (id_insn[4:0] == `OR1200_ALUOP_SUB)
`endif
`ifdef OR1200_IMPL_ALU_EXT
`else
		| (id_insn[4:0] == `OR1200_ALUOP_EXTHB)
		| (id_insn[4:0] == `OR1200_ALUOP_EXTW)
`endif
		;
 
		// Illegal and OR1200 unsupported instructions
	default:
		except_illegal <=  1'b1;
 
	endcase
	end // if (!ex_freeze)
end
 
 
//
// Decode of alu_op
//
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE)
		alu_op <=  `OR1200_ALUOP_NOP;
	else if (!ex_freeze & id_freeze | ex_flushpipe)
		alu_op <=  `OR1200_ALUOP_NOP;
	else if (!ex_freeze) begin
	  case (id_insn[31:26])		// synopsys parallel_case
 
	    // l.movhi
	    `OR1200_OR32_MOVHI:
	      alu_op <=  `OR1200_ALUOP_MOVHI;
 
	    // l.addi
	    `OR1200_OR32_ADDI:
	      alu_op <=  `OR1200_ALUOP_ADD;
 
	    // l.addic
	    `OR1200_OR32_ADDIC:
	      alu_op <=  `OR1200_ALUOP_ADDC;
 
	    // l.andi
	    `OR1200_OR32_ANDI:
	      alu_op <=  `OR1200_ALUOP_AND;
 
	    // l.ori
	    `OR1200_OR32_ORI:
	      alu_op <=  `OR1200_ALUOP_OR;
 
	    // l.xori
	    `OR1200_OR32_XORI:
	      alu_op <=  `OR1200_ALUOP_XOR;
 
	    // l.muli
`ifdef OR1200_MULT_IMPLEMENTED
	    `OR1200_OR32_MULI:
	      alu_op <=  `OR1200_ALUOP_MUL;
`endif
 
	    // Shift and rotate insns with immediate
	    `OR1200_OR32_SH_ROTI:
	      alu_op <=  `OR1200_ALUOP_SHROT;
 
	    // SFXX insns with immediate
	    `OR1200_OR32_SFXXI:
	      alu_op <=  `OR1200_ALUOP_COMP;
 
	    // ALU instructions except the one with immediate
	    `OR1200_OR32_ALU:
	      alu_op <=  {1'b0,id_insn[3:0]};
 
	    // SFXX instructions
	    `OR1200_OR32_SFXX:
	      alu_op <=  `OR1200_ALUOP_COMP;
`ifdef OR1200_IMPL_ALU_CUST5	    
	    // l.cust5
	    `OR1200_OR32_CUST5:
	      alu_op <=  `OR1200_ALUOP_CUST5;
`endif	    
	    // Default
	    default: begin
	      alu_op <=  `OR1200_ALUOP_NOP;
	    end
 
	  endcase
 
	end
end
 
 
//
// Decode of second ALU operation field [9:6]
//
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE)
		alu_op2 <=  0;
	else if (!ex_freeze & id_freeze | ex_flushpipe)
	        alu_op2 <= 0;
   	else if (!ex_freeze) begin
		alu_op2 <=  id_insn[`OR1200_ALUOP2_POS];
	end
end
 
//
// Decode of spr_read, spr_write
//
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE) begin
		spr_read <=  1'b0;
		spr_write <=  1'b0;
	end
	else if (!ex_freeze & id_freeze | ex_flushpipe) begin
		spr_read <=  1'b0;
		spr_write <=  1'b0;
	end
	else if (!ex_freeze) begin
		case (id_insn[31:26])     // synopsys parallel_case
 
		// l.mfspr
		`OR1200_OR32_MFSPR: begin
			spr_read <=  1'b1;
			spr_write <=  1'b0;
		end
 
		// l.mtspr
		`OR1200_OR32_MTSPR: begin
			spr_read <=  1'b0;
			spr_write <=  1'b1;
		end
 
		// Default
		default: begin
			spr_read <=  1'b0;
			spr_write <=  1'b0;
		end
 
		endcase
	end
end
 
//
// Decode of mac_op
//
`ifdef OR1200_MAC_IMPLEMENTED
always @(id_insn) begin
	case (id_insn[31:26])		// synopsys parallel_case
 
	// l.maci
	`OR1200_OR32_MACI:
		id_mac_op =  `OR1200_MACOP_MAC;
 
	// l.mac, l.msb
	`OR1200_OR32_MACMSB:
		id_mac_op =  id_insn[2:0];
 
	// Illegal and OR1200 unsupported instructions
	default:
		id_mac_op =  `OR1200_MACOP_NOP;
 
	endcase
end
 
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE)
		ex_mac_op <=  `OR1200_MACOP_NOP;
	else if (!ex_freeze & id_freeze | ex_flushpipe)
		ex_mac_op <=  `OR1200_MACOP_NOP;
	else if (!ex_freeze)
		ex_mac_op <=  id_mac_op;
end
 
assign mac_op = abort_mvspr ? `OR1200_MACOP_NOP : ex_mac_op;
`else
assign id_mac_op = `OR1200_MACOP_NOP;
assign mac_op = `OR1200_MACOP_NOP;
`endif
 
 
//
// Decode of rfwb_op
//
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE)
		rfwb_op <=  `OR1200_RFWBOP_NOP;
	else  if (!ex_freeze & id_freeze | ex_flushpipe)
		rfwb_op <=  `OR1200_RFWBOP_NOP;
	else  if (!ex_freeze) begin
		case (id_insn[31:26])		// synopsys parallel_case
 
		// j.jal
		`OR1200_OR32_JAL:
			rfwb_op <=  {`OR1200_RFWBOP_LR, 1'b1};
 
		// j.jalr
		`OR1200_OR32_JALR:
			rfwb_op <=  {`OR1200_RFWBOP_LR, 1'b1};
 
		// l.movhi
		`OR1200_OR32_MOVHI:
			rfwb_op <=  {`OR1200_RFWBOP_ALU, 1'b1};
 
		// l.mfspr
		`OR1200_OR32_MFSPR:
			rfwb_op <=  {`OR1200_RFWBOP_SPRS, 1'b1};
 
		// l.lwz
		`OR1200_OR32_LWZ:
			rfwb_op <=  {`OR1200_RFWBOP_LSU, 1'b1};
 
		// l.lbz
		`OR1200_OR32_LBZ:
			rfwb_op <=  {`OR1200_RFWBOP_LSU, 1'b1};
 
		// l.lbs
		`OR1200_OR32_LBS:
			rfwb_op <=  {`OR1200_RFWBOP_LSU, 1'b1};
 
		// l.lhz
		`OR1200_OR32_LHZ:
			rfwb_op <=  {`OR1200_RFWBOP_LSU, 1'b1};
 
		// l.lhs
		`OR1200_OR32_LHS:
			rfwb_op <=  {`OR1200_RFWBOP_LSU, 1'b1};
 
		// l.addi
		`OR1200_OR32_ADDI:
			rfwb_op <=  {`OR1200_RFWBOP_ALU, 1'b1};
 
		// l.addic
		`OR1200_OR32_ADDIC:
			rfwb_op <=  {`OR1200_RFWBOP_ALU, 1'b1};
 
		// l.andi
		`OR1200_OR32_ANDI:
			rfwb_op <=  {`OR1200_RFWBOP_ALU, 1'b1};
 
		// l.ori
		`OR1200_OR32_ORI:
			rfwb_op <=  {`OR1200_RFWBOP_ALU, 1'b1};
 
		// l.xori
		`OR1200_OR32_XORI:
			rfwb_op <=  {`OR1200_RFWBOP_ALU, 1'b1};
 
		// l.muli
`ifdef OR1200_MULT_IMPLEMENTED
		`OR1200_OR32_MULI:
			rfwb_op <=  {`OR1200_RFWBOP_ALU, 1'b1};
`endif
 
		// Shift and rotate insns with immediate
		`OR1200_OR32_SH_ROTI:
			rfwb_op <=  {`OR1200_RFWBOP_ALU, 1'b1};
 
		// ALU instructions except the one with immediate
		`OR1200_OR32_ALU:
			rfwb_op <=  {`OR1200_RFWBOP_ALU, 1'b1};
 
`ifdef OR1200_ALU_IMPL_CUST5
		// l.cust5 instructions
		`OR1200_OR32_CUST5:
			rfwb_op <=  {`OR1200_RFWBOP_ALU, 1'b1};
`endif
`ifdef OR1200_FPU_IMPLEMENTED
		  // FPU instructions, lf.XXX.s, except sfxx
		  `OR1200_OR32_FLOAT:
		    rfwb_op <=  {`OR1200_RFWBOP_FPU,!id_insn[3]};
`endif
		// Instructions w/o register-file write-back
		default: 
			rfwb_op <=  `OR1200_RFWBOP_NOP;
 
 
		endcase
	end
end
 
//
// Decode of id_branch_op
//
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE)
		id_branch_op <=  `OR1200_BRANCHOP_NOP;
	else if (id_flushpipe)
		id_branch_op <=  `OR1200_BRANCHOP_NOP;
	else if (!id_freeze) begin
		case (if_insn[31:26])		// synopsys parallel_case
 
		// l.j
		`OR1200_OR32_J:
			id_branch_op <=  `OR1200_BRANCHOP_J;
 
		// j.jal
		`OR1200_OR32_JAL:
			id_branch_op <=  `OR1200_BRANCHOP_J;
 
		// j.jalr
		`OR1200_OR32_JALR:
			id_branch_op <=  `OR1200_BRANCHOP_JR;
 
		// l.jr
		`OR1200_OR32_JR:
			id_branch_op <=  `OR1200_BRANCHOP_JR;
 
		// l.bnf
		`OR1200_OR32_BNF:
			id_branch_op <=  `OR1200_BRANCHOP_BNF;
 
		// l.bf
		`OR1200_OR32_BF:
			id_branch_op <=  `OR1200_BRANCHOP_BF;
 
		// l.rfe
		`OR1200_OR32_RFE:
			id_branch_op <=  `OR1200_BRANCHOP_RFE;
 
		// Non branch instructions
		default:
			id_branch_op <=  `OR1200_BRANCHOP_NOP;
 
		endcase
	end
end
 
//
// Generation of ex_branch_op
//
always @(posedge clk or `OR1200_RST_EVENT rst)
	if (rst == `OR1200_RST_VALUE)
		ex_branch_op <=  `OR1200_BRANCHOP_NOP;
	else if (!ex_freeze & id_freeze | ex_flushpipe)
		ex_branch_op <=  `OR1200_BRANCHOP_NOP;		
	else if (!ex_freeze)
		ex_branch_op <=  id_branch_op;
 
//
// Decode of id_lsu_op
//
always @(id_insn) begin
	case (id_insn[31:26])		// synopsys parallel_case
 
	// l.lwz
	`OR1200_OR32_LWZ:
		id_lsu_op =  `OR1200_LSUOP_LWZ;
 
	// l.lbz
	`OR1200_OR32_LBZ:
		id_lsu_op =  `OR1200_LSUOP_LBZ;
 
	// l.lbs
	`OR1200_OR32_LBS:
		id_lsu_op =  `OR1200_LSUOP_LBS;
 
	// l.lhz
	`OR1200_OR32_LHZ:
		id_lsu_op =  `OR1200_LSUOP_LHZ;
 
	// l.lhs
	`OR1200_OR32_LHS:
		id_lsu_op =  `OR1200_LSUOP_LHS;
 
	// l.sw
	`OR1200_OR32_SW:
		id_lsu_op =  `OR1200_LSUOP_SW;
 
	// l.sb
	`OR1200_OR32_SB:
		id_lsu_op =  `OR1200_LSUOP_SB;
 
	// l.sh
	`OR1200_OR32_SH:
		id_lsu_op =  `OR1200_LSUOP_SH;
 
	// Non load/store instructions
	default:
		id_lsu_op =  `OR1200_LSUOP_NOP;
 
	endcase
end
 
//
// Decode of comp_op
//
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE) begin
		comp_op <=  4'd0;
	end else if (!ex_freeze & id_freeze | ex_flushpipe)
		comp_op <=  4'd0;
	else if (!ex_freeze)
		comp_op <=  id_insn[24:21];
end
 
`ifdef OR1200_FPU_IMPLEMENTED
//
// Decode of FPU ops
//
   assign fpu_op = {(id_insn[31:26] == `OR1200_OR32_FLOAT), 
		    id_insn[`OR1200_FPUOP_WIDTH-2:0]};
`else
   assign fpu_op = {`OR1200_FPUOP_WIDTH{1'b0}};
`endif
 
 
//
// Decode of l.sys
//
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE)
		sig_syscall <=  1'b0;
	else if (!ex_freeze & id_freeze | ex_flushpipe)
		sig_syscall <=  1'b0;
	else if (!ex_freeze) begin
`ifdef OR1200_VERBOSE
// synopsys translate_off
		if (id_insn[31:23] == {`OR1200_OR32_XSYNC, 3'b000})
			$display("Generating sig_syscall");
// synopsys translate_on
`endif
		sig_syscall <=  (id_insn[31:23] == {`OR1200_OR32_XSYNC, 3'b000});
	end
end
 
//
// Decode of l.trap
//
always @(posedge clk or `OR1200_RST_EVENT rst) begin
	if (rst == `OR1200_RST_VALUE)
		sig_trap <=  1'b0;
	else if (!ex_freeze & id_freeze | ex_flushpipe)
		sig_trap <=  1'b0;
	else if (!ex_freeze) begin
`ifdef OR1200_VERBOSE
// synopsys translate_off
		if (id_insn[31:23] == {`OR1200_OR32_XSYNC, 3'b010})
			$display("Generating sig_trap");
// synopsys translate_on
`endif
		sig_trap <=  (id_insn[31:23] == {`OR1200_OR32_XSYNC, 3'b010})
			| du_hwbkpt;
	end
end
 
// Decode destination register address for data cache to check if store ops
// are being done from the stack register (r1) or frame pointer register (r2)
`ifdef OR1200_DC_NOSTACKWRITETHROUGH   
always @(posedge clk or `OR1200_RST_EVENT rst) begin
   if (rst == `OR1200_RST_VALUE)
     dc_no_writethrough <= 0;
   else if (!ex_freeze)
     dc_no_writethrough <= (id_insn[20:16] == 5'd1) | (id_insn[20:16] == 5'd2);
end
`else
 
   assign dc_no_writethrough = 0;
 
`endif      
 
endmodule