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microwatt/uart16550/raminfr.v

112 lines
5.6 KiB
Verilog

//////////////////////////////////////////////////////////////////////
//// ////
//// raminfr.v ////
//// ////
//// ////
//// This file is part of the "UART 16550 compatible" project ////
//// http://www.opencores.org/cores/uart16550/ ////
//// ////
//// Documentation related to this project: ////
//// - http://www.opencores.org/cores/uart16550/ ////
//// ////
//// Projects compatibility: ////
//// - WISHBONE ////
//// RS232 Protocol ////
//// 16550D uart (mostly supported) ////
//// ////
//// Overview (main Features): ////
//// Inferrable Distributed RAM for FIFOs ////
//// ////
//// Known problems (limits): ////
//// None . ////
//// ////
//// To Do: ////
//// Nothing so far. ////
//// ////
//// Author(s): ////
//// - gorban@opencores.org ////
//// - Jacob Gorban ////
//// ////
//// Created: 2002/07/22 ////
//// Last Updated: 2002/07/22 ////
//// (See log for the revision history) ////
//// ////
//// ////
//////////////////////////////////////////////////////////////////////
//// ////
//// Copyright (C) 2000, 2001 Authors ////
//// ////
//// 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 ////
//// ////
//////////////////////////////////////////////////////////////////////
//
// CVS Revision History
//
// $Log: not supported by cvs2svn $
// Revision 1.1 2002/07/22 23:02:23 gorban
// Bug Fixes:
// * Possible loss of sync and bad reception of stop bit on slow baud rates fixed.
// Problem reported by Kenny.Tung.
// * Bad (or lack of ) loopback handling fixed. Reported by Cherry Withers.
//
// Improvements:
// * Made FIFO's as general inferrable memory where possible.
// So on FPGA they should be inferred as RAM (Distributed RAM on Xilinx).
// This saves about 1/3 of the Slice count and reduces P&R and synthesis times.
//
// * Added optional baudrate output (baud_o).
// This is identical to BAUDOUT* signal on 16550 chip.
// It outputs 16xbit_clock_rate - the divided clock.
// It's disabled by default. Define UART_HAS_BAUDRATE_OUTPUT to use.
//
//Following is the Verilog code for a dual-port RAM with asynchronous read.
module raminfr
(clk, we, a, dpra, di, dpo);
parameter addr_width = 4;
parameter data_width = 8;
parameter depth = 16;
input clk;
input we;
input [addr_width-1:0] a;
input [addr_width-1:0] dpra;
input [data_width-1:0] di;
//output [data_width-1:0] spo;
output [data_width-1:0] dpo;
reg [data_width-1:0] ram [depth-1:0];
wire [data_width-1:0] dpo;
wire [data_width-1:0] di;
wire [addr_width-1:0] a;
wire [addr_width-1:0] dpra;
always @(posedge clk) begin
if (we)
ram[a] <= di;
end
// assign spo = ram[a];
assign dpo = ram[dpra];
endmodule