//======================================================================
//
// tb_uart.v
// ---------
// Testbench for the UART core.
//
//
// Author: Joachim Strombergson
// Copyright (c) 2014, SUNET
// All rights reserved.
//
// 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.
//
//======================================================================
//------------------------------------------------------------------
// Simulator directives.
//------------------------------------------------------------------
`timescale 1ns/10ps
module tb_uart();
//----------------------------------------------------------------
// Internal constant and parameter definitions.
//----------------------------------------------------------------
parameter DEBUG = 0;
parameter VERBOSE = 0;
parameter CLK_HALF_PERIOD = 1;
parameter CLK_PERIOD = CLK_HALF_PERIOD * 2;
//----------------------------------------------------------------
// Register and Wire declarations.
//----------------------------------------------------------------
reg [31 : 0] cycle_ctr;
reg [31 : 0] error_ctr;
reg [31 : 0] tc_ctr;
reg tb_clk;
reg tb_reset_n;
reg tb_rxd;
wire tb_txd;
wire tb_rxd_syn;
wire [7 : 0] tb_rxd_data;
wire tb_rxd_ack;
wire tb_txd_syn;
wire [7 : 0] tb_txd_data;
wire tb_txd_ack;
reg tb_cs;
reg tb_we;
reg [3 : 0] tb_address;
reg [31 : 0] tb_write_data;
wire [31 : 0] tb_read_data;
wire tb_error;
wire [7 : 0] tb_debug;
reg txd_state;
//----------------------------------------------------------------
// Device Under Test.
//----------------------------------------------------------------
uart dut(
.clk(tb_clk),
.reset_n(tb_reset_n),
.rxd(tb_rxd),
.txd(tb_txd),
.rxd_syn(tb_rxd_syn),
.rxd_data(tb_rxd_data),
.rxd_ack(tb_rxd_ack),
// Internal transmit interface.
.txd_syn(tb_txd_syn),
.txd_data(tb_txd_data),
.txd_ack(tb_txd_ack),
// API interface.
.cs(tb_cs),
.we(tb_we),
.address(tb_address),
.write_data(tb_write_data),
.read_data(tb_read_data),
.error(tb_error),
.debug(tb_debug)
);
//----------------------------------------------------------------
// Concurrent assignments.
//----------------------------------------------------------------
// We connect the internal facing ports on the dut together.
assign tb_txd_syn = tb_rxd_syn;
assign tb_txd_data = tb_rxd_data;
assign tb_rxd_ack = tb_txd_ack;
//----------------------------------------------------------------
// clk_gen
//
// Clock generator process.
//----------------------------------------------------------------
always
begin : clk_gen
#CLK_HALF_PERIOD tb_clk = !tb_clk;
end // clk_gen
//----------------------------------------------------------------
// sys_monitor
//----------------------------------------------------------------
always
begin : sys_monitor
#(CLK_PERIOD);
if (DEBUG)
begin
dump_rx_state();
dump_tx_state();
$display("");
end
if (VERBOSE)
begin
$display("cycle: 0x%016x", cycle_ctr);
end
cycle_ctr = cycle_ctr + 1;
end
//----------------------------------------------------------------
// tx_monitor
//
// Observes what happens on the dut tx port and reports it.
//----------------------------------------------------------------
always @*
begin : tx_monitor
if ((!tb_txd) && txd_state)
begin
$display("txd going low.");
txd_state = 0;
end
if (tb_txd && (!txd_state))
begin
$display("txd going high");
txd_state = 1;
end
end
//----------------------------------------------------------------
// dump_dut_state()
//
// Dump the state of the dut when needed.
//----------------------------------------------------------------
task dump_dut_state();
begin
$display("State of DUT");
$display("------------");
$display("Inputs and outputs:");
$display("rxd = 0x%01x, txd = 0x%01x,",
dut.core.rxd, dut.core.txd);
$display("");
$display("Sample and data registers:");
$display("rxd_reg = 0x%01x, rxd_byte_reg = 0x%01x",
dut.core.rxd_reg, dut.core.rxd_byte_reg);
$display("");
$display("Counters:");
$display("rxd_bit_ctr_reg = 0x%01x, rxd_bitrate_ctr_reg = 0x%02x",
dut.core.rxd_bit_ctr_reg, dut.core.rxd_bitrate_ctr_reg);
$display("");
$display("Control signals and FSM state:");
$display("erx_ctrl_reg = 0x%02x",
dut.core.erx_ctrl_reg);
$display("");
end
endtask // dump_dut_state
//----------------------------------------------------------------
// dump_rx_state()
//
// Dump the state of the rx engine.
//----------------------------------------------------------------
task dump_rx_state();
begin
$display("rxd = 0x%01x, rxd_reg = 0x%01x, rxd_byte_reg = 0x%01x, rxd_bit_ctr_reg = 0x%01x, rxd_bitrate_ctr_reg = 0x%02x, rxd_syn = 0x%01x, erx_ctrl_reg = 0x%02x",
dut.core.rxd, dut.core.rxd_reg, dut.core.rxd_byte_reg, dut.core.rxd_bit_ctr_reg,
dut.core.rxd_bitrate_ctr_reg, dut.core.rxd_syn, dut.core.erx_ctrl_reg);
end
endtask // dump_dut_state
//----------------------------------------------------------------
// dump_tx_state()
//
// Dump the state of the tx engine.
//----------------------------------------------------------------
task dump_tx_state();
begin
$display("txd = 0x%01x, txd_reg = 0x%01x, txd_byte_reg = 0x%01x, txd_bit_ctr_reg = 0x%01x, txd_bitrate_ctr_reg = 0x%02x, txd_ack = 0x%01x, etx_ctrl_reg = 0x%02x",
dut.core.txd, dut.core.txd_reg, dut.core.txd_byte_reg, dut.core.txd_bit_ctr_reg,
dut.core.txd_bitrate_ctr_reg, dut.core.txd_ack, dut.core.etx_ctrl_reg);
end
endtask // dump_dut_state
//----------------------------------------------------------------
// reset_dut()
//----------------------------------------------------------------
task reset_dut();
begin
$display("*** Toggle reset.");
tb_reset_n = 0;
#(2 * CLK_PERIOD);
tb_reset_n = 1;
end
endtask // reset_dut
//----------------------------------------------------------------
// init_sim()
//
// Initialize all counters and testbed functionality as well
// as setting the DUT inputs to defined values.
//----------------------------------------------------------------
task init_sim();
begin
cycle_ctr = 0;
error_ctr = 0;
tc_ctr = 0;
tb_clk = 0;
tb_reset_n = 1;
tb_rxd = 1;
tb_cs = 0;
tb_we = 0;
tb_address = 4'h0;
tb_write_data = 32'h00000000;
txd_state = 1;
end
endtask // init_sim
//----------------------------------------------------------------
// transmit_byte
//
// Transmit a byte of data to the DUT receive port.
//----------------------------------------------------------------
task transmit_byte(input [7 : 0] data);
integer i;
begin
$display("*** Transmitting byte 0x%02x to the dut.", data);
#10;
// Start bit
$display("*** Transmitting start bit.");
tb_rxd = 0;
#(CLK_PERIOD * dut.core.DEFAULT_CLK_RATE);
// Send the bits LSB first.
for (i = 0 ; i < 8 ; i = i + 1)
begin
$display("*** Transmitting data[%1d] = 0x%01x.", i, data[i]);
tb_rxd = data[i];
#(CLK_PERIOD * dut.core.DEFAULT_CLK_RATE);
end
// Send two stop bits. I.e. two bit times high (mark) value.
$display("*** Transmitting two stop bits.");
tb_rxd = 1;
#(2 * CLK_PERIOD * dut.core.DEFAULT_CLK_RATE * dut.core.DEFAULT_STOP_BITS);
$display("*** End of transmission.");
end
endtask // transmit_byte
//----------------------------------------------------------------
// check_transmit
//
// Transmits a byte and checks that it was captured internally
// by the dut.
//----------------------------------------------------------------
task check_transmit(input [7 : 0] data);
begin
tc_ctr = tc_ctr + 1;
transmit_byte(data);
if (dut.core.rxd_byte_reg == data)
begin
$display("*** Correct data: 0x%01x captured by the dut.",
dut.core.rxd_byte_reg);
end
else
begin
$display("*** Incorrect data: 0x%01x captured by the dut Should be: 0x%01x.",
dut.core.rxd_byte_reg, data);
error_ctr = error_ctr + 1;
end
end
endtask // check_transmit
//----------------------------------------------------------------
// test_transmit
//
// Transmit a number of test bytes to the dut.
//----------------------------------------------------------------
task test_transmit();
begin
check_transmit(8'h55);
check_transmit(8'h42);
check_transmit(8'hde);
check_transmit(8'had);
end
endtask // test_transmit
//----------------------------------------------------------------
// display_test_result()
//
// Display the accumulated test results.
//----------------------------------------------------------------
task display_test_result();
begin
if (error_ctr == 0)
begin
$display("*** All %02d test cases completed successfully", tc_ctr);
end
else
begin
$display("*** %02d test cases did not complete successfully.", error_ctr);
end
end
endtask // display_test_result
//----------------------------------------------------------------
// uart_test
// The main test functionality.
//----------------------------------------------------------------
initial
begin : uart_test
$display(" -- Testbench for uart core started --");
init_sim();
dump_dut_state();
reset_dut();
dump_dut_state();
test_transmit();
display_test_result();
$display("*** Simulation done.");
$finish;
end // uart_test
endmodule // tb_uart
//======================================================================
// EOF tb_uart.v
//======================================================================
