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

//

//  WISHBONE revB.2 compliant Programable Interrupt Timer - Top-level

//

//  Author: Bob Hayes

//          rehayes@opencores.org

//

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

//

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

// Copyright (c) 2009, Robert Hayes

//

// All rights reserved.

//

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are met:

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

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

//     * 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.

//     * 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.

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

// 45678901234567890123456789012345678901234567890123456789012345678901234567890

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

                 parameter PRE_COUNT_SIZE = 15,  // Prescale Counter size

                 parameter COUNT_SIZE = 16,      // Main counter size

                 parameter DECADE_CNTR = 1'b1,   // Prescale rollover decode

                 parameter NO_PRESCALE = 1'b0,   // Remove prescale function

                 parameter SINGLE_CYCLE = 1'b0,  // No bus wait state added

                 parameter DWIDTH = 16)          // Data bus width

  (

  // Wishbone Signals

  output [DWIDTH-1:0] wb_dat_o,     // databus output

  output              wb_ack_o,     // bus cycle acknowledge output

  input               wb_clk_i,     // master clock input

  input               wb_rst_i,     // synchronous active high reset

  input               arst_i,       // asynchronous reset

  input         [2:0] wb_adr_i,     // lower address bits

  input  [DWIDTH-1:0] wb_dat_i,     // databus input

  input               wb_we_i,      // write enable input

  input               wb_stb_i,     // stobe/core select signal

  input               wb_cyc_i,     // valid bus cycle input

  input         [1:0] wb_sel_i,     // Select byte in word bus transaction

  // PIT IO Signals

  output              pit_o,        // PIT output pulse

  output              pit_irq_o,    // PIT interrupt request signal output

  output              cnt_flag_o,   // PIT Flag Out

  output              cnt_sync_o,   // PIT Master Enable for Slave PIT's

  input               ext_sync_i    // Counter enable from Master PIT

  );

  wire [COUNT_SIZE-1:0] mod_value;     // Main Counter Modulo

  wire [COUNT_SIZE-1:0] cnt_n;         // PIT Counter Value

  wire                  async_rst_b;   // Asyncronous reset

  wire                  sync_reset;    // Syncronous reset

  wire           [ 3:0] write_regs;    // Control register write strobes

  wire                  prescale_out;  //

  wire                  pit_flg_clr;   // Clear PIT Rollover Status Bit

  wire                  pit_slave;     // PIT in Slave Mode, ext_sync_i selected

  wire           [ 3:0] pit_pre_scl;   // Prescaler modulo

  wire                  counter_sync;  // 

  // Wishbone Bus interface

  pit_wb_bus #(.ARST_LVL(ARST_LVL),

               .SINGLE_CYCLE(SINGLE_CYCLE),

               .DWIDTH(DWIDTH))

    wishbone(

    .wb_dat_o     ( wb_dat_o ),

    .wb_ack_o     ( wb_ack_o ),

    .wb_clk_i     ( wb_clk_i ),

    .wb_rst_i     ( wb_rst_i ),

    .arst_i       ( arst_i ),

    .wb_adr_i     ( wb_adr_i ),

    .wb_dat_i     ( wb_dat_i ),

    .wb_we_i      ( wb_we_i ),

    .wb_stb_i     ( wb_stb_i ),

    .wb_cyc_i     ( wb_cyc_i ),

    .wb_sel_i     ( wb_sel_i ),

    // outputs

    .write_regs   ( write_regs ),

    .sync_reset   ( sync_reset ),

    // inputs    

    .async_rst_b  ( async_rst_b ),

    .irq_source   ( cnt_flag_o ),

    .read_regs    (               // in  -- status register bits

                   { cnt_n,

                     mod_value,

                     {pit_slave, DECADE_CNTR, NO_PRESCALE, 1'b0, pit_pre_scl,

                      5'b0, cnt_flag_o, pit_ien, cnt_sync_o}

                   }

                  )

  );

// -----------------------------------------------------------------------------

  pit_regs #(.ARST_LVL(ARST_LVL),

             .COUNT_SIZE(COUNT_SIZE),

             .NO_PRESCALE(NO_PRESCALE),

             .DWIDTH(DWIDTH))

    regs(

    // outputs

    .mod_value    ( mod_value ),

    .pit_pre_scl  ( pit_pre_scl ),

    .pit_slave    ( pit_slave ),

    .pit_flg_clr  ( pit_flg_clr ),

    .pit_ien      ( pit_ien ),

    .cnt_sync_o   ( cnt_sync_o ),

    .pit_irq_o    ( pit_irq_o ),

    // inputs

    .async_rst_b  ( async_rst_b ),

    .sync_reset   ( sync_reset ),

    .bus_clk      ( wb_clk_i ),

    .write_bus    ( wb_dat_i ),

    .write_regs   ( write_regs ),

    .cnt_flag_o   ( cnt_flag_o )

  );

// -----------------------------------------------------------------------------

  pit_prescale #(.COUNT_SIZE(PRE_COUNT_SIZE),

                 .DECADE_CNTR(DECADE_CNTR),

                 .NO_PRESCALE(NO_PRESCALE))

    prescale(

    // outputs

    .prescale_out      ( prescale_out ),

    .counter_sync      ( counter_sync ),

    // inputs

    .async_rst_b       ( async_rst_b ),

    .sync_reset        ( sync_reset ),

    .bus_clk           ( wb_clk_i ),

    .cnt_sync_o        ( cnt_sync_o ),

    .ext_sync_i        ( ext_sync_i ),

    .pit_slave         ( pit_slave ),

    .divisor           ( pit_pre_scl )

  );

// -----------------------------------------------------------------------------

  pit_count #(.COUNT_SIZE(COUNT_SIZE))

    counter(

    // outputs

    .cnt_n             ( cnt_n ),

    .cnt_flag_o        ( cnt_flag_o ),

    .pit_o             ( pit_o ),

    // inputs

    .async_rst_b       ( async_rst_b ),

    .sync_reset        ( sync_reset ),

    .bus_clk           ( wb_clk_i ),

    .counter_sync      ( counter_sync ),

    .prescale_out      ( prescale_out ),

    .pit_flg_clr       ( pit_flg_clr ),

    .mod_value         ( mod_value )

  );

endmodule // pit_top