flash_loader.v

/*
* Used for loading byte-by-byte game data from SPI flash
* from a given offset
*/

module flash_loader
(
  input  clock,
  input  reset,
  
  input  reload,
  input  [3:0] index,
  
  //Flash load interface
  output flash_csn,
  output flash_sck,
  output flash_mosi,
  input  flash_miso,

  output [7:0] load_write_data,
  output data_valid
);


`ifndef SIM
localparam [23:0] FLASH_BEGIN_ADDR = 24'h200000;
`else
localparam [23:0] FLASH_BEGIN_ADDR = 24'h000000;
`endif


reg load_done;
reg [21:0] load_addr; // Support games up to 1MB (MSB=1 ends)

wire flashmem_valid = !load_done;
wire flashmem_ready;
assign data_valid = flashmem_ready;
wire [23:0] flashmem_addr = (FLASH_BEGIN_ADDR + (index_lat << 18)) | {load_addr};
reg [3:0] index_lat;
reg load_done_pre;

// Flash memory load interface
always @(posedge clock) 
begin
  if (reset == 1'b1) begin
    load_done_pre <= 1'b0;
    load_done <= 1'b0;
    load_addr <= 0;
    index_lat <= 4'h0;
  end else begin
    if (reload == 1'b1) begin
      load_done_pre <= 1'b0;
      load_done <= 1'b0;
      load_addr <= 0;
      index_lat <= index;
    end else begin
      if(!load_done_pre) begin
        if (flashmem_ready == 1'b1) begin
          if (load_addr[$bits(load_addr)-1]) begin
            load_done_pre <= 1'b1;
          end else 
            load_addr <= load_addr + 1;
        end
      end else begin
        if (load_addr[9] == 0)
          load_addr <= load_addr + 1;
        else
          load_done <= 1'b1;
      end
    end
  end
end

flashmem
flashmem_i
(
  .clk(clock),
  .reset(reset),
  .valid(flashmem_valid),
  .ready(flashmem_ready),
  .addr(flashmem_addr),
  .rdata(load_write_data),

  .spi_cs(flash_csn),
  .spi_sclk(flash_sck),
  .spi_mosi(flash_mosi),
  .spi_miso(flash_miso)
);

endmodule