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[/] [amber/] [trunk/] [hw/] [vlog/] [amber25/] [a25_fetch.v] - Rev 35
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////////////////////////////////////////////////////////////////// // // // Fetch - Instantiates the fetch stage sub-modules of // // the Amber 25 Core // // // // This file is part of the Amber project // // http://www.opencores.org/project,amber // // // // Description // // Instantiates the Cache and Wishbone I/F // // Also contains a little bit of logic to decode memory // // accesses to decide if they are cached or not // // // // Author(s): // // - Conor Santifort, csantifort.amber@gmail.com // // // ////////////////////////////////////////////////////////////////// // // // Copyright (C) 2011 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 a25_fetch ( input i_clk, input i_mem_stall, input i_exec_stall, input i_conflict, // Decode stage stall pipeline because of an instruction conflict output o_fetch_stall, // when this is asserted all registers // in decode and exec stages are frozen input i_system_rdy, // External system can stall core with this signal input [31:0] i_iaddress, input i_iaddress_valid, input [31:0] i_iaddress_nxt, // un-registered version of address to the cache rams output [31:0] o_fetch_instruction, input i_cache_enable, // cache enable input i_cache_flush, // cache flush input [31:0] i_cacheable_area, // each bit corresponds to 2MB address space output o_wb_req, output [31:0] o_wb_address, input [127:0] i_wb_read_data, input i_wb_ready ); `include "memory_configuration.v" wire core_stall; wire cache_stall; wire [127:0] cache_read_data128; wire [31:0] cache_read_data; wire sel_cache; wire uncached_instruction_read; wire address_cachable; wire icache_wb_req; wire wait_wb; reg wb_req_r = 'd0; wire [31:0] wb_rdata32; // ====================================== // Memory Decode // ====================================== assign address_cachable = in_cachable_mem( i_iaddress ) && i_cacheable_area[i_iaddress[25:21]]; assign sel_cache = address_cachable && i_iaddress_valid && i_cache_enable; // Don't start wishbone transfers when the cache is stalling the core // The cache stalls the core during its initialization sequence assign uncached_instruction_read = !sel_cache && i_iaddress_valid && !(cache_stall); // Return read data either from the wishbone bus or the cache assign cache_read_data = i_iaddress[3:2] == 2'd0 ? cache_read_data128[ 31: 0] : i_iaddress[3:2] == 2'd1 ? cache_read_data128[ 63:32] : i_iaddress[3:2] == 2'd2 ? cache_read_data128[ 95:64] : cache_read_data128[127:96] ; assign wb_rdata32 = i_iaddress[3:2] == 2'd0 ? i_wb_read_data[ 31: 0] : i_iaddress[3:2] == 2'd1 ? i_wb_read_data[ 63:32] : i_iaddress[3:2] == 2'd2 ? i_wb_read_data[ 95:64] : i_wb_read_data[127:96] ; assign o_fetch_instruction = sel_cache ? cache_read_data : uncached_instruction_read ? wb_rdata32 : 32'hffeeddcc ; // Stall the instruction decode and execute stages of the core // when the fetch stage needs more than 1 cycle to return the requested // read data assign o_fetch_stall = !i_system_rdy || wait_wb || cache_stall; assign o_wb_address = i_iaddress; assign o_wb_req = icache_wb_req || uncached_instruction_read; assign wait_wb = (o_wb_req || wb_req_r) && !i_wb_ready; always @(posedge i_clk) wb_req_r <= o_wb_req && !i_wb_ready; assign core_stall = o_fetch_stall || i_mem_stall || i_exec_stall || i_conflict; // ====================================== // L1 Instruction Cache // ====================================== a25_icache u_cache ( .i_clk ( i_clk ), .i_core_stall ( core_stall ), .o_stall ( cache_stall ), .i_select ( sel_cache ), .i_address ( i_iaddress ), .i_address_nxt ( i_iaddress_nxt ), .i_cache_enable ( i_cache_enable ), .i_cache_flush ( i_cache_flush ), .o_read_data ( cache_read_data128 ), .o_wb_req ( icache_wb_req ), .i_wb_read_data ( i_wb_read_data ), .i_wb_ready ( i_wb_ready ) ); endmodule
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