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[/] [amber/] [trunk/] [hw/] [vlog/] [amber25/] [a25_wishbone.v] - Rev 56
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////////////////////////////////////////////////////////////////// // // // Wishbone master interface for the Amber 25 core // // // // This file is part of the Amber project // // http://www.opencores.org/project,amber // // // // Description // // Turns memory access requests from the execute stage and // // instruction and data caches into wishbone bus cycles. // // For 4-word read requests from either cache and swap // // accesses ( read followed by write to the same address) // // from the execute stage, a block transfer is done. // // All other requests result in single word transfers. // // // // Write accesses can be done in a single clock cycle on // // the wishbone bus, is the destination allows it. The // // next transfer will begin immediately on the // // next cycle on the bus. This looks like a block transfer // // and does hold ownership of the wishbone bus, preventing // // the other master ( the ethernet MAC) from gaining // // ownership between those two cycles. But otherwise it would // // be necessary to insert a wait cycle after every write, // // slowing down the performance of the core by around 5 to // // 10%. // // // // 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 // // // ////////////////////////////////////////////////////////////////// // TODO add support for exclusive accesses module a25_wishbone ( input i_clk, // Port 0 - dcache uncached input i_port0_req, output o_port0_ack, input i_port0_write, input [127:0] i_port0_wdata, input [15:0] i_port0_be, input [31:0] i_port0_addr, output [127:0] o_port0_rdata, // Port 1 - dcache cached input i_port1_req, output o_port1_ack, input i_port1_write, input [127:0] i_port1_wdata, input [15:0] i_port1_be, input [31:0] i_port1_addr, output [127:0] o_port1_rdata, // Port 2 - instruction cache accesses, read only input i_port2_req, output o_port2_ack, input i_port2_write, input [127:0] i_port2_wdata, input [15:0] i_port2_be, input [31:0] i_port2_addr, output [127:0] o_port2_rdata, // 128-bit Wishbone Bus output reg [31:0] o_wb_adr = 'd0, output reg [15:0] o_wb_sel = 'd0, output reg o_wb_we = 'd0, output reg [127:0] o_wb_dat = 'd0, output reg o_wb_cyc = 'd0, output reg o_wb_stb = 'd0, input [127:0] i_wb_dat, input i_wb_ack, input i_wb_err ); // ---------------------------------------------------- // Parameters // ---------------------------------------------------- localparam WBUF = 3; // ---------------------------------------------------- // Signals // ---------------------------------------------------- wire [0:0] wbuf_valid [WBUF-1:0]; wire [0:0] wbuf_accepted [WBUF-1:0]; wire [0:0] wbuf_write [WBUF-1:0]; wire [127:0] wbuf_wdata [WBUF-1:0]; wire [15:0] wbuf_be [WBUF-1:0]; wire [31:0] wbuf_addr [WBUF-1:0]; wire [0:0] wbuf_rdata_valid [WBUF-1:0]; wire new_access; reg [WBUF-1:0] serving_port = 'd0; // ---------------------------------------------------- // Instantiate the write buffers // ---------------------------------------------------- a25_wishbone_buf u_a25_wishbone_buf_p0 ( .i_clk ( i_clk ), .i_req ( i_port0_req ), .o_ack ( o_port0_ack ), .i_write ( i_port0_write ), .i_wdata ( i_port0_wdata ), .i_be ( i_port0_be ), .i_addr ( i_port0_addr ), .o_rdata ( o_port0_rdata ), .o_valid ( wbuf_valid [0] ), .i_accepted ( wbuf_accepted [0] ), .o_write ( wbuf_write [0] ), .o_wdata ( wbuf_wdata [0] ), .o_be ( wbuf_be [0] ), .o_addr ( wbuf_addr [0] ), .i_rdata ( i_wb_dat ), .i_rdata_valid ( wbuf_rdata_valid [0] ) ); a25_wishbone_buf u_a25_wishbone_buf_p1 ( .i_clk ( i_clk ), .i_req ( i_port1_req ), .o_ack ( o_port1_ack ), .i_write ( i_port1_write ), .i_wdata ( i_port1_wdata ), .i_be ( i_port1_be ), .i_addr ( i_port1_addr ), .o_rdata ( o_port1_rdata ), .o_valid ( wbuf_valid [1] ), .i_accepted ( wbuf_accepted [1] ), .o_write ( wbuf_write [1] ), .o_wdata ( wbuf_wdata [1] ), .o_be ( wbuf_be [1] ), .o_addr ( wbuf_addr [1] ), .i_rdata ( i_wb_dat ), .i_rdata_valid ( wbuf_rdata_valid [1] ) ); a25_wishbone_buf u_a25_wishbone_buf_p2 ( .i_clk ( i_clk ), .i_req ( i_port2_req ), .o_ack ( o_port2_ack ), .i_write ( i_port2_write ), .i_wdata ( i_port2_wdata ), .i_be ( i_port2_be ), .i_addr ( i_port2_addr ), .o_rdata ( o_port2_rdata ), .o_valid ( wbuf_valid [2] ), .i_accepted ( wbuf_accepted [2] ), .o_write ( wbuf_write [2] ), .o_wdata ( wbuf_wdata [2] ), .o_be ( wbuf_be [2] ), .o_addr ( wbuf_addr [2] ), .i_rdata ( i_wb_dat ), .i_rdata_valid ( wbuf_rdata_valid [2] ) ); assign new_access = !o_wb_stb || i_wb_ack; assign wbuf_accepted[0] = new_access && wbuf_valid[0]; assign wbuf_accepted[1] = new_access && !wbuf_valid[0] && wbuf_valid[1]; assign wbuf_accepted[2] = new_access && !wbuf_valid[0] && !wbuf_valid[1] && wbuf_valid[2]; always @(posedge i_clk) begin if (new_access) begin if (wbuf_valid[0]) begin o_wb_adr <= wbuf_addr [0]; o_wb_sel <= wbuf_be [0]; o_wb_we <= wbuf_write[0]; o_wb_dat <= wbuf_wdata[0]; o_wb_cyc <= 1'd1; o_wb_stb <= 1'd1; serving_port <= 3'b001; end else if (wbuf_valid[1]) begin o_wb_adr <= wbuf_addr [1]; o_wb_sel <= wbuf_be [1]; o_wb_we <= wbuf_write[1]; o_wb_dat <= wbuf_wdata[1]; o_wb_cyc <= 1'd1; o_wb_stb <= 1'd1; serving_port <= 3'b010; end else if (wbuf_valid[2]) begin o_wb_adr <= wbuf_addr [2]; o_wb_sel <= wbuf_be [2]; o_wb_we <= wbuf_write[2]; o_wb_dat <= wbuf_wdata[2]; o_wb_cyc <= 1'd1; o_wb_stb <= 1'd1; serving_port <= 3'b100; end else begin o_wb_cyc <= 1'd0; o_wb_stb <= 1'd0; // Don't need to change these values because they are ignored // when stb is low, but it makes for a cleaner waveform, at the expense of a few gates o_wb_we <= 1'd0; o_wb_adr <= 'd0; o_wb_dat <= 'd0; serving_port <= 3'b000; end end end assign {wbuf_rdata_valid[2], wbuf_rdata_valid[1], wbuf_rdata_valid[0]} = {3{i_wb_ack & ~ o_wb_we}} & serving_port; endmodule
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