// File:  loopback.v// Date:  01/01/2005// Name:  Eric Crabill// // This is the top level design for the// EE178 Lab #4 assignment.// The `timescale directive specifies what// the simulation time units are (1 ns here)// and what the simulator timestep should be// (1 ps here).`timescale 1 ns / 1 psmodule loopback(clk, rst, leds, switches, rs232_tx, rs232_rx, lock);  input         clk, rst;  output  [7:0] leds;  input   [7:0] switches;  input         rs232_rx;  output        rs232_tx;  output        lock;  // Instantiate PicoBlaze and the instruction  // ROM.  This is simply cut and paste from the  // example designs that come with PicoBlaze.  // Interrupts are not used for this design.  wire    [9:0] address;  wire   [17:0] instruction;  wire    [7:0] port_id;  wire    [7:0] out_port;  reg     [7:0] in_port;  wire          write_strobe;  wire          read_strobe;    wire rst_in;  wire clk50MHz;    assign rst_in = ~rst;  kcpsm3 my_kcpsm3 (    .address(address),    .instruction(instruction),    .port_id(port_id),    .write_strobe(write_strobe),    .out_port(out_port),    .read_strobe(read_strobe),    .in_port(in_port),    .interrupt(1'b0),    .interrupt_ack(),    .reset(rst_in),    .clk(clk50MHz)    );program my_program (    .clka(clk50MHz),    .addra(address),    .douta(instruction),    .clkb(1'b0),    .addrb(10'b0000000000),    .doutb());	   my_dcm instance_name (    .CLKIN_IN(clk),     .RST_IN(rst_in),     .CLKFX_OUT(clk50MHz),     .CLKIN_IBUFG_OUT(),     .CLK0_OUT(),     .LOCKED_OUT(lock)    );  // Implement the 16x bit rate counter  // for the uart transmit and receive.  // The system clock is 50 MHz, and the  // desired baud rate is 9600.  I used  // the formula in the documentation to  // calculate the terminal count value.  reg     [8:0] baud_count;  reg           en_16_x_baud;  always @(posedge clk50MHz or posedge rst_in)  begin    if (rst_in)    begin      baud_count <= 0;      en_16_x_baud <= 0;    end    else    begin      if (baud_count == 325)      begin        baud_count <= 0;        en_16_x_baud <= 1;      end      else      begin        baud_count <= baud_count + 1;        en_16_x_baud <= 0;      end    end  end  // Implement the output port logic:  // leds_out, port 01  // uart_data_tx, port 03  wire          write_to_uart;  wire          write_to_leds;  wire          buffer_full;  reg     [7:0] leds;  assign write_to_uart = write_strobe & (port_id == 8'h03);  assign write_to_leds = write_strobe & (port_id == 8'h01);  always @(posedge clk50MHz or posedge rst_in)  begin    if (rst_in) leds <= 0;    else if (write_to_leds) leds <= out_port;  end  uart_tx transmit (    .data_in(out_port),     .write_buffer(write_to_uart),    .reset_buffer(rst_in),    .en_16_x_baud(en_16_x_baud),    .serial_out(rs232_tx),    .buffer_full(buffer_full),    .buffer_half_full(),    .clk(clk50MHz)    );  // Implement the input port logic:  // switch_in, port 00  // uart_data_rx, port 02  // data_present, port 04  // buffer_full, port 05  reg           read_from_uart;  wire    [7:0] rx_data;  wire          data_present;  always @(posedge clk50MHz or posedge rst_in)  begin    if (rst_in)    begin      in_port <= 0;      read_from_uart <= 0;    end    else    begin      case (port_id)        8'h00: in_port <= switches;        8'h02: in_port <= rx_data;        8'h04: in_port <= {7'b0000000, data_present};        8'h05: in_port <= {7'b0000000, buffer_full};        default: in_port <= 8'h00;      endcase      read_from_uart <= read_strobe & (port_id == 8'h02);    end  end  uart_rx receive (    .serial_in(rs232_rx),    .data_out(rx_data),    .read_buffer(read_from_uart),    .reset_buffer(rst_in),    .en_16_x_baud(en_16_x_baud),    .buffer_data_present(data_present),    .buffer_full(),    .buffer_half_full(),    .clk(clk50MHz)    );  endmodule