// Example code for a PicoRV32 AHBLite System-on-Chip
//  Iain McNally
//  ECS, University of Soutampton
//
//
// This version supports 3 AHBLite slaves:
//
//  ahb_ram           RAM
//  ahb_switches      A handshaking interface to support input from switches and buttons
//  ahb_out           An output interface supporting simultaneous update of data and valid signals
//

module soc(

  input HCLK, HRESETn,
  
  input [15:0] Switches, 
  input [1:0] Buttons, 

  output [15:0] DataOut,
  output DataValid,
  output LOCKUP

);
 
timeunit 1ns;
timeprecision 100ps;

  // Global & Master AHB Signals
  wire [31:0] HADDR, HWDATA, HRDATA;
  wire [1:0] HTRANS;
  wire [2:0] HSIZE, HBURST;
  wire [3:0] HPROT;
  wire HWRITE, HMASTLOCK, HRESP, HREADY;

  // Per-Slave AHB Signals
  wire HSEL_RAM, HSEL_SW, HSEL_DOUT;
  wire [31:0] HRDATA_RAM, HRDATA_SW, HRDATA_DOUT;
  wire HREADYOUT_RAM, HREADYOUT_SW, HREADYOUT_DOUT;

  // Set this to zero because PicoRV32 does not support LOCKUP
  assign LOCKUP = '0;

  // Set this to zero because simple slaves do not generate errors
  assign HRESP = '0;

  // PicoRV32 is AHB Master
  picorv32_ahb riscv_1 (

    // AHB Signals
    .HCLK, .HRESETn,
    .HADDR, .HBURST, .HMASTLOCK, .HPROT, .HSIZE, .HTRANS, .HWDATA, .HWRITE,
    .HRDATA, .HREADY, .HRESP                                   

  );


  // AHB interconnect including address decoder, register and multiplexer
  ahb_interconnect interconnect_1 (

    .HCLK, .HRESETn, .HADDR, .HRDATA, .HREADY,

    .HSEL_SIGNALS({HSEL_DOUT,HSEL_SW,HSEL_RAM}),
    .HRDATA_SIGNALS({HRDATA_DOUT,HRDATA_SW,HRDATA_RAM}),
    .HREADYOUT_SIGNALS({HREADYOUT_DOUT,HREADYOUT_SW,HREADYOUT_RAM})

  );


  // AHBLite Slaves
        
  ahb_ram ram_1 (

    .HCLK, .HRESETn, .HADDR, .HWDATA, .HSIZE, .HTRANS, .HWRITE, .HREADY,
    .HSEL(HSEL_RAM),
    .HRDATA(HRDATA_RAM), .HREADYOUT(HREADYOUT_RAM)

  );

  ahb_switches switches_1 (

    .HCLK, .HRESETn, .HADDR, .HWDATA, .HSIZE, .HTRANS, .HWRITE, .HREADY,
    .HSEL(HSEL_SW),
    .HRDATA(HRDATA_SW), .HREADYOUT(HREADYOUT_SW),

    .Switches(Switches), .Buttons(Buttons)

  );

  ahb_out out_1 (

    .HCLK, .HRESETn, .HADDR, .HWDATA, .HSIZE, .HTRANS, .HWRITE, .HREADY,
    .HSEL(HSEL_DOUT),
    .HRDATA(HRDATA_DOUT), .HREADYOUT(HREADYOUT_DOUT),

    .DataOut(DataOut), .DataValid(DataValid)

  );

  //-------------------------
  // Assertions which should be valid for all systems:
  //

  // Control signals from master should never be undefined
  HTRANS_defined:
    assert property(@(posedge HCLK) disable iff (!HRESETn)
      ( ! $isunknown(HTRANS) )
    ) else $error("HTRANS is undefined: %b", HTRANS);

  HWRITE_defined:
    assert property(@(posedge HCLK) disable iff (!HRESETn)
      ( ! $isunknown(HWRITE) )
    ) else $error("HWRITE is undefined");

  HSIZE_defined:
    assert property(@(posedge HCLK) disable iff (!HRESETn)
      ( ! $isunknown(HSIZE) )
    ) else $error("HSIZE is undefined: %b", HSIZE);

  HADDR_defined:
    assert property(@(posedge HCLK) disable iff (!HRESETn)
      ( ! $isunknown(HADDR) )
    ) else $error("HADDR is undefined: %b", HADDR);

  // Data signal from master should be defined during write
  HWDATA_defined:
    assert property(@(posedge HCLK) disable iff (!HRESETn)
      (HWRITE && HREADY) |=> ( ! $isunknown(HWDATA) )
    ) else $error("HWDATA is undefined during write data phase: %b", HWDATA);


endmodule