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//////////////////////////////////////////////////////////////////
//                                                              //
//  Co-processor module for Amber 2 Core                        //
//                                                              //
//  This file is part of the Amber project                      //
//  http://www.opencores.org/project,amber                      //
//                                                              //
//  Description                                                 //
//  Co_processor 15 registers and control signals               //                                                           //
//  Author(s):                                                  //
//      - Conor Santifort, csantifort.amber@gmail.com           //
//                                                              //
//////////////////////////////////////////////////////////////////
//                                                              //
// Copyright (C) 2010 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                     //
//                                                              //
//////////////////////////////////////////////////////////////////
 
 
module a23_coprocessor
(
input                       i_clk,
input                       i_fetch_stall,    // stall all stages of the cpu at the same time
input       [2:0]           i_copro_opcode1,
input       [2:0]           i_copro_opcode2,
input       [3:0]           i_copro_crn,      // Register Number 
input       [3:0]           i_copro_crm,
input       [3:0]           i_copro_num,
input       [1:0]           i_copro_operation,
input       [31:0]          i_copro_write_data,
 
input                       i_fault,          // high to latch the fault address and status
input       [7:0]           i_fault_status,
input       [31:0]          i_fault_address,  // the address that caused the fault
 
output reg  [31:0]          o_copro_read_data,
output                      o_cache_enable,
output                      o_cache_flush,
output      [31:0]          o_cacheable_area 
);
 
// Bit 0 - Cache on(1)/off
// Bit 1 - Shared (1) or seperate User/Supervisor address space
// Bit 2 - address monitor mode(1)
reg [2:0]  cache_control = 3'b000;
 
// Bit 0 - 2MB memory from 0 to 0x01fffff cacheable(1)/not cachable
// Bit 1 - next 2MB region etc.
reg [31:0] cacheable_area = 32'h0;
 
// Marks memory regions as read only so writes are ignored by the cache
// Bit 0 - 2MB memory from 0 to 0x01fffff updateable(1)/not updateable
// Bit 1 - next 2MB region etc.
reg [31:0] updateable_area = 32'h0;
 
// Accesses to a region with a flag set in this register cause the
// cache to flush
// Bit 0 - 2MB memory from 0 to 0x01fffff
// Bit 1 - next 2MB region etc.
reg [31:0] disruptive_area = 32'h0;
 
 
reg [7:0]  fault_status  = 'd0;
reg [31:0] fault_address = 'd0;  // the address that caused the fault
 
wire       copro15_reg1_write;
 
 
// ---------------------------
// Outputs
// ---------------------------
assign o_cache_enable   = cache_control[0];
assign o_cache_flush    = copro15_reg1_write;
assign o_cacheable_area = cacheable_area;
 
// ---------------------------
// Capture an access fault address and status
// ---------------------------
always @ ( posedge i_clk )
    if ( !i_fetch_stall )
        begin
        if ( i_fault )
            begin
 
            `ifdef A23_COPRO15_DEBUG    
            $display ("Fault status  set to 0x%08x", i_fault_status);
            $display ("Fault address set to 0x%08x", i_fault_address);
            `endif        
            fault_status    <= i_fault_status;
            fault_address   <= i_fault_address;
            end
        end
 
 
// ---------------------------
// Register Writes
// ---------------------------
always @ ( posedge i_clk )
    if ( !i_fetch_stall )         
        begin
        if ( i_copro_operation == 2'd2 )
            case ( i_copro_crn )
                4'd2: cache_control   <= i_copro_write_data[2:0];
                4'd3: cacheable_area  <= i_copro_write_data[31:0];
                4'd4: updateable_area <= i_copro_write_data[31:0];
                4'd5: disruptive_area <= i_copro_write_data[31:0];
            endcase
        end
 
// Flush the cache
assign copro15_reg1_write = !i_fetch_stall && i_copro_operation == 2'd2 && i_copro_crn == 4'd1;
 
 
// ---------------------------
// Register Reads   
// ---------------------------
always @ ( posedge i_clk )        
    if ( !i_fetch_stall )
        case ( i_copro_crn )
            // ID Register - [31:24] Company id, [23:16] Manuf id, [15:8] Part type, [7:0] revision
            4'd0:    o_copro_read_data <= 32'h4156_0300;
            4'd2:    o_copro_read_data <= {29'd0, cache_control}; 
            4'd3:    o_copro_read_data <= cacheable_area; 
            4'd4:    o_copro_read_data <= updateable_area; 
            4'd5:    o_copro_read_data <= disruptive_area; 
            4'd6:    o_copro_read_data <= {24'd0, fault_status };
            4'd7:    o_copro_read_data <= fault_address;
            default: o_copro_read_data <= 32'd0;
        endcase
 
 
 
// ========================================================
// Debug code - not synthesizable
// ========================================================
 
`ifdef A23_COPRO15_DEBUG    
//synopsys translate_off
reg [1:0]  copro_operation_d1;
reg [3:0]  copro_crn_d1;
 
always @( posedge i_clk )
    if ( !i_fetch_stall )
        begin
        copro_operation_d1  <= i_copro_operation;
        copro_crn_d1        <= i_copro_crn;
        end
 
always @( posedge i_clk )
    if ( !i_fetch_stall )
        begin
        if ( i_copro_operation == 2'd2 )  // mcr
            case ( i_copro_crn )
                4'd 1: begin `TB_DEBUG_MESSAGE $display ("Write 0x%08h to   Co-Pro 15 #1, Flush Cache", i_copro_write_data); end
                4'd 2: begin `TB_DEBUG_MESSAGE $display ("Write 0x%08h to   Co-Pro 15 #2, Cache Control", i_copro_write_data); end
                4'd 3: begin `TB_DEBUG_MESSAGE $display ("Write 0x%08h to   Co-Pro 15 #3, Cacheable area", i_copro_write_data); end
                4'd 4: begin `TB_DEBUG_MESSAGE $display ("Write 0x%08h to   Co-Pro 15 #4, Updateable area", i_copro_write_data); end
                4'd 5: begin `TB_DEBUG_MESSAGE $display ("Write 0x%08h to   Co-Pro 15 #5, Disruptive area", i_copro_write_data); end
            endcase
 
        if ( copro_operation_d1 == 2'd1 ) // mrc
            case ( copro_crn_d1 )
                4'd 0: begin `TB_DEBUG_MESSAGE $display ("Read  0x%08h from Co-Pro 15 #0, ID Register", o_copro_read_data); end
                4'd 2: begin `TB_DEBUG_MESSAGE $display ("Read  0x%08h from Co-Pro 15 #2, Cache control", o_copro_read_data); end
                4'd 3: begin `TB_DEBUG_MESSAGE $display ("Read  0x%08h from Co-Pro 15 #3, Cacheable area", o_copro_read_data); end
                4'd 4: begin `TB_DEBUG_MESSAGE $display ("Read  0x%08h from Co-Pro 15 #4, Updateable area", o_copro_read_data); end
                4'd 5: begin `TB_DEBUG_MESSAGE $display ("Read  0x%08h from Co-Pro 15 #4, Disruptive area", o_copro_read_data); end
                4'd 6: begin `TB_DEBUG_MESSAGE $display ("Read  0x%08h from Co-Pro 15 #6, Fault Status Register", o_copro_read_data); end
                4'd 7: begin `TB_DEBUG_MESSAGE $display ("Read  0x%08h from Co-Pro 15 #7, Fault Address Register", o_copro_read_data); end
            endcase
    end
//synopsys translate_on
`endif
 
endmodule