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//======================================================================
//
// uart.v
// ------
// Configuration registers for the uart core.
//
//
// Author: Joachim Strombergson
// Copyright (c) 2014, SUNET
//
// Redistribution and use in source and binary forms, with or
// without modification, are permitted provided that the following
// conditions are met:
//
// 1. Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in
// the documentation and/or other materials provided with the
// distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
// ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
//======================================================================
module comm_regs
(
input wire clk,
input wire rst,
input wire cs,
input wire we,
input wire [ 7 : 0] address,
input wire [31 : 0] write_data,
output wire [31 : 0] read_data,
output wire error
);
//----------------------------------------------------------------
// Internal constant and parameter definitions.
//----------------------------------------------------------------
// API addresses.
localparam ADDR_CORE_NAME0 = 8'h00;
localparam ADDR_CORE_NAME1 = 8'h01;
localparam ADDR_CORE_TYPE = 8'h02;
localparam ADDR_CORE_VERSION = 8'h03;
localparam ADDR_BIT_RATE = 8'h10;
localparam ADDR_DATA_BITS = 8'h11;
localparam ADDR_STOP_BITS = 8'h12;
// Core ID constants.
localparam CORE_NAME0 = 32'h75617274; // "uart"
localparam CORE_NAME1 = 32'h20202020; // " "
localparam CORE_TYPE = 32'h20202031; // " 1"
localparam CORE_VERSION = 32'h302e3031; // "0.01"
// The default bit rate is based on target clock frequency
// divided by the bit rate times in order to hit the
// center of the bits. I.e.
// Clock: 50 MHz, 9600 bps
// Divisor = 50*10E6 / 9600 = 5208
localparam DEFAULT_BIT_RATE = 16'd5208;
localparam DEFAULT_DATA_BITS = 4'h8;
localparam DEFAULT_STOP_BITS = 2'h1;
//----------------------------------------------------------------
// Registers including update variables and write enable.
//----------------------------------------------------------------
reg [31: 0] tmp_read_data;
//----------------------------------------------------------------
// Concurrent connectivity for ports etc.
//----------------------------------------------------------------
assign read_data = tmp_read_data;
//----------------------------------------------------------------
// Access Handler
//----------------------------------------------------------------
always @ (posedge clk or posedge rst)
begin
if (rst)
begin
terasic_top.bit_rate <= DEFAULT_BIT_RATE;
terasic_top.data_bits <= DEFAULT_DATA_BITS;
terasic_top.stop_bits <= DEFAULT_STOP_BITS;
end
else if (cs && we)
begin
// write operations
case (address)
ADDR_BIT_RATE:
terasic_top.bit_rate <= write_data[15 : 0];
ADDR_DATA_BITS:
terasic_top.data_bits <= write_data[3 : 0];
ADDR_STOP_BITS:
terasic_top.stop_bits <= write_data[1 : 0];
endcase
end
end
always @*
begin
tmp_read_data = 32'h00000000;
if (cs && !we)
begin
// read operations
case (address)
ADDR_CORE_NAME0:
tmp_read_data = CORE_NAME0;
ADDR_CORE_NAME1:
tmp_read_data = CORE_NAME1;
ADDR_CORE_TYPE:
tmp_read_data = CORE_TYPE;
ADDR_CORE_VERSION:
tmp_read_data = CORE_VERSION;
ADDR_BIT_RATE:
tmp_read_data = {16'h0000, terasic_top.bit_rate};
ADDR_DATA_BITS:
tmp_read_data = {28'h0000000, terasic_top.data_bits};
ADDR_STOP_BITS:
tmp_read_data = {30'h0000000, terasic_top.stop_bits};
endcase
end
end
endmodule // uart
//======================================================================
// EOF uart.v
//======================================================================
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