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////////////////////////////////////////////////////////////////////////////////

//

//  Computer Operating Properly - XGATE interrupt encoder

//

//  Author: Bob Hayes

//          rehayes@opencores.org

//

//  Downloaded from: http://www.opencores.org/projects/xgate.....

//

////////////////////////////////////////////////////////////////////////////////

// Copyright (c) 2009, Robert Hayes

//

// This source file is free software: you can redistribute it and/or modify

// it under the terms of the GNU Lesser General Public License as published

// by the Free Software Foundation, either version 3 of the License, or

// (at your option) any later version.

//

// Supplemental terms.

//     * Redistributions of source code must retain the above copyright

//       notice, this list of conditions and the following disclaimer.

//     * Neither the name of the <organization> nor the

//       names of its contributors may be used to endorse or promote products

//       derived from this software without specific prior written permission.

//

// THIS SOFTWARE IS PROVIDED BY Robert Hayes ''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 Robert Hayes 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.

//

// You should have received a copy of the GNU General Public License

// along with this program.  If not, see <http://www.gnu.org/licenses/>.

////////////////////////////////////////////////////////////////////////////////

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module xgate_irq_encode #(parameter MAX_CHANNEL = 127)    // Max XGATE Interrupt Channel Number

(

  output reg          [ 6:0] int_req,     // Encoded interrupt request to RISC

  output     [MAX_CHANNEL:1] xgif,        // Interrupt outputs to Host

  input      [MAX_CHANNEL:1] chan_req_i,  // XGATE Interrupt requests from peropherials

  input      [MAX_CHANNEL:1] chan_bypass, // XGATE Interrupt bypass

  input      [MAX_CHANNEL:1] xgif_status  // Interrupt outputs from RISC core

);

  wire [MAX_CHANNEL:1] chan_ena_gate;  // Ouptut of channel enable gating

  // Pass non-bypassed interrupt inputs to XGATE RISC

  assign chan_ena_gate = ~chan_bypass & chan_req_i;

  // Set int_reg to the index of the index of the lowest chan_req_i input that is active

  integer i = 0;

  always @(chan_ena_gate)

    begin

      int_req = 0;

        for (i = MAX_CHANNEL; i >= 1; i = i - 1)

          if (chan_ena_gate[i] == 1'b1)

            int_req = i;

    end

  // XGATE output interrupt mux

  assign xgif = (chan_bypass & chan_req_i) | (~chan_bypass & xgif_status);

endmodule  // xgate_irq_encode