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////////////////////////////////////////////////////////////////////////////////
//
// Filename: memdev.v
//
// Project: dbgbus, a collection of 8b channel to WB bus debugging protocols
//
// Purpose: This file is really simple: it creates an on-chip memory,
// accessible via the wishbone bus, that can be used in this
// project. The memory has single cycle pipeline access, although the
// memory pipeline here still costs a cycle and there may be other cycles
// lost between the ZipCPU (or whatever is the master of the bus) and this,
// thus costing more cycles in access. Either way, operations can be
// pipelined for single cycle access on subsequent transactions.
//
//
// Creator: Dan Gisselquist, Ph.D.
// Gisselquist Technology, LLC
//
////////////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 2015-2017, Gisselquist Technology, LLC
//
// This file is part of the debugging interface demonstration.
//
// The debugging interface demonstration is free software (firmware): 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
// 3 of the License, or (at your option) any later version.
//
// This debugging interface demonstration is distributed in the hope that it
// will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty
// of MERCHANTIBILITY 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 program. (It's in the $(ROOT)/doc directory. Run make
// with no target there if the PDF file isn't present.) If not, see
// <http://www.gnu.org/licenses/> for a copy.
//
// License: LGPL, v3, as defined and found on www.gnu.org,
// http://www.gnu.org/licenses/lgpl.html
//
//
////////////////////////////////////////////////////////////////////////////////
//
//
module memdev(i_clk, i_wb_cyc, i_wb_stb, i_wb_we, i_wb_addr, i_wb_data, i_wb_sel,
o_wb_ack, o_wb_stall, o_wb_data);
parameter LGMEMSZ=15, DW=32, EXTRACLOCK= 0;
localparam AW = LGMEMSZ - 2;
input wire i_clk, i_wb_cyc, i_wb_stb, i_wb_we;
input wire [(AW-1):0] i_wb_addr;
input wire [(DW-1):0] i_wb_data;
input wire [(DW/8-1):0] i_wb_sel;
output reg o_wb_ack;
output wire o_wb_stall;
output reg [(DW-1):0] o_wb_data;
wire w_wstb, w_stb;
wire [(DW-1):0] w_data;
wire [(AW-1):0] w_addr;
wire [(DW/8-1):0] w_sel;
generate
if (EXTRACLOCK == 0)
begin
assign w_wstb = (i_wb_stb)&&(i_wb_we);
assign w_stb = i_wb_stb;
assign w_addr = i_wb_addr;
assign w_data = i_wb_data;
assign w_sel = i_wb_sel;
end else begin
reg last_wstb, last_stb;
always @(posedge i_clk)
last_wstb <= (i_wb_stb)&&(i_wb_we);
always @(posedge i_clk)
last_stb <= (i_wb_stb);
reg [(AW-1):0] last_addr;
reg [(DW-1):0] last_data;
reg [(DW/8-1):0] last_sel;
always @(posedge i_clk)
last_data <= i_wb_data;
always @(posedge i_clk)
last_addr <= i_wb_addr;
always @(posedge i_clk)
last_sel <= i_wb_sel;
assign w_wstb = last_wstb;
assign w_stb = last_stb;
assign w_addr = last_addr;
assign w_data = last_data;
assign w_sel = last_sel;
end endgenerate
reg [(DW-1):0] mem [0:((1<<AW)-1)];
always @(posedge i_clk)
o_wb_data <= mem[w_addr];
always @(posedge i_clk)
begin
if ((w_wstb)&&(w_sel[3]))
mem[w_addr][31:24] <= w_data[31:24];
if ((w_wstb)&&(w_sel[2]))
mem[w_addr][23:16] <= w_data[23:16];
if ((w_wstb)&&(w_sel[1]))
mem[w_addr][15: 8] <= w_data[15:8];
if ((w_wstb)&&(w_sel[0]))
mem[w_addr][ 7: 0] <= w_data[7:0];
end
always @(posedge i_clk)
o_wb_ack <= (w_stb);
assign o_wb_stall = 1'b0;
// Now, let's keep verilator happy
// verilator lint_off UNUSED
wire unused;
assign unused = i_wb_cyc;
// verilator lint_on UNUSED
endmodule