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

//

//  Computer Operating Properly - Control registers

//

//  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/>.

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

// 45678901234567890123456789012345678901234567890123456789012345678901234567890

module xgate_regs #(parameter ARST_LVL = 1'b0,    // asynchronous reset level

                    parameter MAX_CHANNEL = 127)  // Max XGATE Interrupt Channel Number

  (

  output reg                  xge,          // XGATE Module Enable

  output reg                  xgfrz,        // Stop XGATE in Freeze Mode

  output reg                  xgdbg_set,    // Enter XGATE Debug Mode

  output reg                  xgdbg_clear,  // Leave XGATE Debug Mode

  output reg                  xgss,         // XGATE Single Step

  output reg                  xgfact,       // XGATE Flag Activity

  output reg                  xgsweif_c,    // Clear XGATE Software Error Interrupt FLag

  output reg                  xgie,         // XGATE Interrupt Enable

  output reg           [15:1] xgvbr,        // XGATE vector Base Address Register

  output reg           [ 7:0] xgswt,        // XGATE Software Trigger Register for host

  output reg           [15:0] xgisp74,      // XGATE Interrupt level 7-4 stack pointer

  output reg           [15:0] xgisp30,      // XGATE Interrupt level 3-0 stack pointer

  output reg                  clear_xgif_7,    // Strobe for decode to clear interrupt flag bank 7

  output reg                  clear_xgif_6,    // Strobe for decode to clear interrupt flag bank 6

  output reg                  clear_xgif_5,    // Strobe for decode to clear interrupt flag bank 5

  output reg                  clear_xgif_4,    // Strobe for decode to clear interrupt flag bank 4

  output reg                  clear_xgif_3,    // Strobe for decode to clear interrupt flag bank 3

  output reg                  clear_xgif_2,    // Strobe for decode to clear interrupt flag bank 2

  output reg                  clear_xgif_1,    // Strobe for decode to clear interrupt flag bank 1

  output reg                  clear_xgif_0,    // Strobe for decode to clear interrupt flag bank 0

  output reg           [15:0] clear_xgif_data, // Data for decode to clear interrupt flag

  output                      semaph_stat,     // Return Status of Semaphore bit

  output reg                  brk_irq_ena,     // Enable BRK instruction to generate interrupt

  input                       bus_clk,       // Control register bus clock

  input                       async_rst_b,   // Async reset signal

  input                       sync_reset,    // Syncronous reset signal

  input                [15:0] write_bus,     // Write Data Bus

  input                       write_xgmctl,  // Write Strobe for XGMCTL register

  input                       write_xgisp74, // Write Strobe for XGISP74 register

  input                       write_xgisp30, // Write Strobe for XGISP30 register

  input                       write_xgvbr,   // Write Strobe for XGVBR register

  input                       write_xgif_7,  // Write Strobe for Interrupt Flag Register 7

  input                       write_xgif_6,  // Write Strobe for Interrupt Flag Register 6

  input                       write_xgif_5,  // Write Strobe for Interrupt Flag Register 5

  input                       write_xgif_4,  // Write Strobe for Interrupt Flag Register 4

  input                       write_xgif_3,  // Write Strobe for Interrupt Flag Register 3

  input                       write_xgif_2,  // Write Strobe for Interrupt Flag Register 2

  input                       write_xgif_1,  // Write Strobe for Interrupt Flag Register 1

  input                       write_xgif_0,  // Write Strobe for Interrupt Flag Register 0

  input                       write_xgswt    // Write Strobe for XGSWT register

  );

  // registers

  // Wires

  wire write_any_xgif;

  //

  // module body

  //

  // generate wishbone write registers

  // XGMCTL Register

  always @(posedge bus_clk or negedge async_rst_b)

    if (!async_rst_b)

      begin

        xge         <= 1'b0;

        xgfrz       <= 1'b0;

        xgdbg_set   <= 1'b0;

        xgdbg_clear <= 1'b0;

        xgss        <= 1'b0;

        xgfact      <= 1'b0;

        brk_irq_ena <= 1'b0;

        xgsweif_c   <= 1'b0;

        xgie        <= 1'b0;

       end

    else if (sync_reset)

      begin

        xge         <= 1'b0;

        xgfrz       <= 1'b0;

        xgdbg_set   <= 1'b0;

        xgdbg_clear <= 1'b0;

        xgss        <= 1'b0;

        xgfact      <= 1'b0;

        brk_irq_ena <= 1'b0;

        xgsweif_c   <= 1'b0;

        xgie        <= 1'b0;

     end

    else if (write_xgmctl)

      begin

        xge         <= write_bus[15] ? write_bus[7] : xge;

        xgfrz       <= write_bus[14] ? write_bus[6] : xgfrz;

        xgdbg_set   <= write_bus[13] && write_bus[5];

        xgdbg_clear <= write_bus[13] && !write_bus[5];

        xgss        <= write_bus[12] && write_bus[4];

        xgfact      <= write_bus[11] ? write_bus[3] : xgfact;

        brk_irq_ena <= write_bus[10] ? write_bus[2] : brk_irq_ena;

        xgsweif_c   <= write_bus[ 9] && write_bus[1];

        xgie        <= write_bus[ 8] ? write_bus[0] : xgie;

      end

    else

      begin

        xgss        <= 1'b0;

        xgsweif_c   <= 1'b0;

        xgdbg_set   <= 1'b0;

        xgdbg_clear <= 1'b0;

      end

  // XGVBR Register

  always @(posedge bus_clk or negedge async_rst_b)

    if (!async_rst_b)

      begin

        xgvbr  <= 15'b1111_1110_0000_000;

       end

    else if (sync_reset)

      begin

        xgvbr  <= 15'b1111_1110_0000_000;

      end

    else if (write_xgvbr)

      begin

        xgvbr[15: 1]  <= xge ? 15'b0 : write_bus[15:1];

      end

  // XGISP74 Register

  always @(posedge bus_clk or negedge async_rst_b)

    if (!async_rst_b)

      xgisp74  <= 16'b0;

    else if (sync_reset)

      xgisp74  <= 16'b0;

    else if (write_xgisp74)

      xgisp74  <= xge ? xgisp74 : write_bus;

  // XGISP30 Register

  always @(posedge bus_clk or negedge async_rst_b)

    if (!async_rst_b)

      xgisp30  <= 16'b0;

    else if (sync_reset)

      xgisp30  <= 16'b0;

    else if (write_xgisp30)

      xgisp30  <= xge ? xgisp30 : write_bus;

  // XGIF 7-0 Registers

  assign write_any_xgif = write_xgif_7 || write_xgif_6 || write_xgif_5 || write_xgif_4 ||

                          write_xgif_3 || write_xgif_2 || write_xgif_1 || write_xgif_0;

  // Registers to clear the interrupt flags. Decode a specific interrupt to

  //  clear by ANDing the clear_xgif_x signal with the clear_xgif_data.

  always @(posedge bus_clk or negedge async_rst_b)

    if (!async_rst_b)

      begin

        clear_xgif_7    <= 1'b0;

        clear_xgif_6    <= 1'b0;

        clear_xgif_5    <= 1'b0;

        clear_xgif_4    <= 1'b0;

        clear_xgif_3    <= 1'b0;

        clear_xgif_2    <= 1'b0;

        clear_xgif_1    <= 1'b0;

        clear_xgif_0    <= 1'b0;

        clear_xgif_data <= 16'b0;

      end

    else if (sync_reset)

      begin

        clear_xgif_7    <= 1'b0;

        clear_xgif_6    <= 1'b0;

        clear_xgif_5    <= 1'b0;

        clear_xgif_4    <= 1'b0;

        clear_xgif_3    <= 1'b0;

        clear_xgif_2    <= 1'b0;

        clear_xgif_1    <= 1'b0;

        clear_xgif_0    <= 1'b0;

        clear_xgif_data <= 16'b0;

      end

    else

      begin

        clear_xgif_7    <= write_xgif_7 && (MAX_CHANNEL > 111);

        clear_xgif_6    <= write_xgif_6 && (MAX_CHANNEL > 95);

        clear_xgif_5    <= write_xgif_5 && (MAX_CHANNEL > 79);

        clear_xgif_4    <= write_xgif_4 && (MAX_CHANNEL > 63);

        clear_xgif_3    <= write_xgif_3 && (MAX_CHANNEL > 47);

        clear_xgif_2    <= write_xgif_2 && (MAX_CHANNEL > 31);

        clear_xgif_1    <= write_xgif_1 && (MAX_CHANNEL > 15);

        clear_xgif_0    <= write_xgif_0;

        clear_xgif_data <= write_any_xgif ? write_bus : clear_xgif_data;

      end

  // XGSWT - XGATE Software Trigger Register

  always @(posedge bus_clk or negedge async_rst_b)

    if (!async_rst_b)

      xgswt <= 8'h00;

    else if (sync_reset)

      xgswt <= 8'h00;

    else if (write_xgswt)

      begin

        xgswt[7] <= write_bus[15] ? write_bus[7] : xgswt[7];

        xgswt[6] <= write_bus[14] ? write_bus[6] : xgswt[6];

        xgswt[5] <= write_bus[13] ? write_bus[5] : xgswt[5];

        xgswt[4] <= write_bus[11] ? write_bus[4] : xgswt[4];

        xgswt[3] <= write_bus[12] ? write_bus[3] : xgswt[3];

        xgswt[2] <= write_bus[10] ? write_bus[2] : xgswt[2];

        xgswt[1] <= write_bus[ 9] ? write_bus[1] : xgswt[1];

        xgswt[0] <= write_bus[ 8] ? write_bus[0] : xgswt[0];

      end

endmodule  // xgate_regs