Subversion Repositories usb_fpga_2_14

/*%

   Common communication interface of default firmwares

   Copyright (C) 2009-2017 ZTEX GmbH.

   http://www.ztex.de

   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.

%*/

/*

   Implements the 4 bi-directional GPIO's of the default interface.

   On FX3 outputs on both ends are or-wired.

   Remember (because it's not implemented here) default interface always

   contains a reset signal.

*/

module ezusb_gpio (

        // control signals

        input clk,                      // system clock

        // hardware pins

        inout [3:0] gpio_n,              // wired or: low-active open-drain output

        // interface

        output reg [3:0] in,

        input [3:0] out                  // wired or: GPIO's not used for output should be 0

    );

    assign gpio_n[0] = !out[0] ? 1'bz : 1'b0;

    assign gpio_n[1] = !out[1] ? 1'bz : 1'b0;

    assign gpio_n[2] = !out[2] ? 1'bz : 1'b0;

    assign gpio_n[3] = !out[3] ? 1'bz : 1'b0;

    always @ (posedge clk)

    begin

        in <= ~gpio_n;

    end

endmodule