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uart.sv
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uart.sv
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// Copyright 2018 ETH Zurich and University of Bologna.
// Copyright and related rights are licensed under the Solderpad Hardware
// License, Version 0.51 (the "License"); you may not use this file except in
// compliance with the License. You may obtain a copy of the License at
// http://solderpad.org/licenses/SHL-0.51. Unless required by applicable law
// or agreed to in writing, software, hardware and materials distributed under
// this License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
// CONDITIONS OF ANY KIND, either express or implied. See the License for the
// specific language governing permissions and limitations under the License.
//
// Author: Unknown
// Date: Unknown
// Description: This module takes data over UART and prints them to the console
// A string is printed to the console as soon as a '\n' character is found
interface uart_bus #(
parameter int unsigned BAUD_RATE = 115200,
parameter int unsigned PARITY_EN = 0
)(
input logic rx,
output logic tx,
input logic rx_en
);
/* pragma translate_off */
`ifndef VERILATOR
localparam time BIT_PERIOD = (1000000000 / BAUD_RATE) * 1ns;
logic [7:0] character;
logic [256*8-1:0] stringa;
logic parity;
integer charnum;
integer file;
initial begin
tx = 1'bZ;
file = $fopen("uart", "w");
end
always begin
if (rx_en) begin
@(negedge rx);
#(BIT_PERIOD/2);
for (int i = 0; i <= 7; i++) begin
#BIT_PERIOD character[i] = rx;
end
if (PARITY_EN == 1) begin
// check parity
#BIT_PERIOD parity = rx;
for (int i=7;i>=0;i--) begin
parity = character[i] ^ parity;
end
if (parity == 1'b1) begin
$display("Parity error detected");
end
end
// STOP BIT
#BIT_PERIOD;
$fwrite(file, "%c", character);
stringa[(255-charnum)*8 +: 8] = character;
if (character == 8'h0A || charnum == 254) begin // line feed or max. chars reached
if (character == 8'h0A) begin
stringa[(255-charnum)*8 +: 8] = 8'h0; // null terminate string, replace line feed
end else begin
stringa[(255-charnum-1)*8 +: 8] = 8'h0; // null terminate string
end
$write("[UART]: %s\n", stringa);
charnum = 0;
stringa = "";
end else begin
charnum = charnum + 1;
end
end else begin
charnum = 0;
stringa = "";
#10;
end
end
task send_char(input logic [7:0] c);
int i;
// start bit
tx = 1'b0;
for (i = 0; i < 8; i++) begin
#(BIT_PERIOD);
tx = c[i];
end
// stop bit
#(BIT_PERIOD);
tx = 1'b1;
#(BIT_PERIOD);
endtask
`endif
/* pragma translate_on */
endinterface