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//
// Copyright 2011 Ettus Research LLC
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
module simple_uart
#(parameter CLKDIV_DEFAULT = 16'd0)
(input clk_i, input rst_i,
input we_i, input stb_i, input cyc_i, output reg ack_o,
input [2:0] adr_i, input [31:0] dat_i, output reg [31:0] dat_o,
output rx_int_o, output tx_int_o, output tx_o, input rx_i, output baud_o);
// Register Map
localparam SUART_CLKDIV = 0;
localparam SUART_TXLEVEL = 1;
localparam SUART_RXLEVEL = 2;
localparam SUART_TXCHAR = 3;
localparam SUART_RXCHAR = 4;
wire wb_acc = cyc_i & stb_i; // WISHBONE access
wire wb_wr = wb_acc & we_i; // WISHBONE write access
reg [15:0] clkdiv;
wire [7:0] rx_char;
wire tx_fifo_full, rx_fifo_empty;
wire [5:0] tx_fifo_level, rx_fifo_level;
always @(posedge clk_i)
if (rst_i)
ack_o <= 1'b0;
else
ack_o <= wb_acc & ~ack_o;
always @(posedge clk_i)
if (rst_i)
clkdiv <= CLKDIV_DEFAULT;
else if (wb_wr)
case(adr_i)
SUART_CLKDIV : clkdiv <= dat_i[15:0];
endcase // case(adr_i)
always @(posedge clk_i)
case (adr_i)
SUART_TXLEVEL : dat_o <= tx_fifo_level;
SUART_RXLEVEL : dat_o <= rx_fifo_level;
SUART_RXCHAR : dat_o <= rx_char;
endcase // case(adr_i)
simple_uart_tx simple_uart_tx
(.clk(clk_i),.rst(rst_i),
.fifo_in(dat_i[7:0]),.fifo_write(ack_o && wb_wr && (adr_i == SUART_TXCHAR)),
.fifo_level(tx_fifo_level),.fifo_full(tx_fifo_full),
.clkdiv(clkdiv),.baudclk(baud_o),.tx(tx_o));
simple_uart_rx simple_uart_rx
(.clk(clk_i),.rst(rst_i),
.fifo_out(rx_char),.fifo_read(ack_o && ~wb_wr && (adr_i == SUART_RXCHAR)),
.fifo_level(rx_fifo_level),.fifo_empty(rx_fifo_empty),
.clkdiv(clkdiv),.rx(rx_i));
assign tx_int_o = ~tx_fifo_full;
assign rx_int_o = ~rx_fifo_empty;
endmodule // simple_uart
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