module spi_top
(
  // Wishbone signals
  wb_clk_i, wb_rst_i, wb_adr_i, wb_dat_i, wb_dat_o, wb_sel_i,
  wb_we_i, wb_stb_i, wb_cyc_i, wb_ack_o, wb_err_o, wb_int_o,

  // SPI signals
  ss_pad_o, sclk_pad_o, mosi_pad_o, miso_pad_i
);

  // Wishbone signals
  input                            wb_clk_i;         // master clock input
  input                            wb_rst_i;         // synchronous active high reset
  input                      [4:0] wb_adr_i;         // lower address bits
  input                   [32-1:0] wb_dat_i;         // databus input
  output                  [32-1:0] wb_dat_o;         // databus output
  input                      [3:0] wb_sel_i;         // byte select inputs
  input                            wb_we_i;          // write enable input
  input                            wb_stb_i;         // stobe/core select signal
  input                            wb_cyc_i;         // valid bus cycle input
  output                           wb_ack_o;         // bus cycle acknowledge output
  output                           wb_err_o;         // termination w/ error
  output                           wb_int_o;         // interrupt request signal output
                                                     
  // SPI signals                                     
  output          [`SPI_SS_NB-1:0] ss_pad_o;         // slave select
  output                           sclk_pad_o;       // serial clock
  output                           mosi_pad_o;       // master out slave in
  input                            miso_pad_i;       // master in slave out
                                                     
  reg                     [32-1:0] wb_dat_o;
  reg                              wb_ack_o;
  reg                              wb_int_o;
                                               
  // Internal signals
  reg       [`SPI_DIVIDER_LEN-1:0] divider;          // Divider register
  reg       [`SPI_CTRL_BIT_NB-1:0] ctrl;             // Control and status register
  reg             [`SPI_SS_NB-1:0] ss;               // Slave select register
  reg                     [32-1:0] wb_dat;           // wb data out
  wire         [`SPI_MAX_CHAR-1:0] rx;               // Rx register
  wire                             rx_negedge;       // miso is sampled on negative edge
  wire                             tx_negedge;       // mosi is driven on negative edge
  wire    [`SPI_CHAR_LEN_BITS-1:0] char_len;         // char len
  wire                             go;               // go
  wire                             lsb;              // lsb first on line
  wire                             ie;               // interrupt enable
  wire                             ass;              // automatic slave select
  wire                             spi_divider_sel;  // divider register select
  wire                             spi_ctrl_sel;     // ctrl register select
  wire                       [3:0] spi_tx_sel;       // tx_l register select
  wire                             spi_ss_sel;       // ss register select
  wire                             tip;              // transfer in progress
  wire                             pos_edge;         // recognize posedge of sclk
  wire                             neg_edge;         // recognize negedge of sclk
  wire                             last_bit;         // marks last character bit
  
  // Address decoder
  assign spi_divider_sel = wb_cyc_i & wb_stb_i & (wb_adr_i[`SPI_OFS_BITS] == `SPI_DIVIDE);
  assign spi_ctrl_sel    = wb_cyc_i & wb_stb_i & (wb_adr_i[`SPI_OFS_BITS] == `SPI_CTRL);
  assign spi_tx_sel[0]   = wb_cyc_i & wb_stb_i & (wb_adr_i[`SPI_OFS_BITS] == `SPI_TX_0);
  assign spi_tx_sel[1]   = wb_cyc_i & wb_stb_i & (wb_adr_i[`SPI_OFS_BITS] == `SPI_TX_1);
  assign spi_tx_sel[2]   = wb_cyc_i & wb_stb_i & (wb_adr_i[`SPI_OFS_BITS] == `SPI_TX_2);
  assign spi_tx_sel[3]   = wb_cyc_i & wb_stb_i & (wb_adr_i[`SPI_OFS_BITS] == `SPI_TX_3);
  assign spi_ss_sel      = wb_cyc_i & wb_stb_i & (wb_adr_i[`SPI_OFS_BITS] == `SPI_SS);
  
  // Read from registers
  always @(wb_adr_i or rx or ctrl or divider or ss)
  begin
    case (wb_adr_i[`SPI_OFS_BITS])
`ifdef SPI_MAX_CHAR_128
      `SPI_RX_0:    wb_dat = rx[31:0];
      `SPI_RX_1:    wb_dat = rx[63:32];
      `SPI_RX_2:    wb_dat = rx[95:64];
      `SPI_RX_3:    wb_dat = {{128-`SPI_MAX_CHAR{1'b0}}, rx[`SPI_MAX_CHAR-1:96]};
`else
`ifdef SPI_MAX_CHAR_64
      `SPI_RX_0:    wb_dat = rx[31:0];
      `SPI_RX_1:    wb_dat = {{64-`SPI_MAX_CHAR{1'b0}}, rx[`SPI_MAX_CHAR-1:32]};
      `SPI_RX_2:    wb_dat = 32'b0;
      `SPI_RX_3:    wb_dat = 32'b0;
`else
      `SPI_RX_0:    wb_dat = {{32-`SPI_MAX_CHAR{1'b0}}, rx[`SPI_MAX_CHAR-1:0]};
      `SPI_RX_1:    wb_dat = 32'b0;
      `SPI_RX_2:    wb_dat = 32'b0;
      `SPI_RX_3:    wb_dat = 32'b0;
`endif
`endif
      `SPI_CTRL:    wb_dat = {{32-`SPI_CTRL_BIT_NB{1'b0}}, ctrl};
      `SPI_DIVIDE:  wb_dat = {{32-`SPI_DIVIDER_LEN{1'b0}}, divider};
      `SPI_SS:      wb_dat = {{32-`SPI_SS_NB{1'b0}}, ss};
      default:      wb_dat = 32'bx;
    endcase
  end
  
  // Wb data out
  always @(posedge wb_clk_i)
  begin
    if (wb_rst_i)
      wb_dat_o <= 32'b0;
    else
      wb_dat_o <= wb_dat;
  end
  
  // Wb acknowledge
  always @(posedge wb_clk_i)
  begin
    if (wb_rst_i)
      wb_ack_o <= 1'b0;
    else
      wb_ack_o <= wb_cyc_i & wb_stb_i & ~wb_ack_o;
  end
  
  // Wb error
  assign wb_err_o = 1'b0;
  
  // Interrupt
  always @(posedge wb_clk_i)
  begin
    if (wb_rst_i)
      wb_int_o <= 1'b0;
    else if (ie && tip && last_bit && pos_edge)
      wb_int_o <= 1'b1;
    else if (wb_ack_o)
      wb_int_o <= 1'b0;
  end
  
  // Divider register
  always @(posedge wb_clk_i)
  begin
    if (wb_rst_i)
        divider <= {`SPI_DIVIDER_LEN{1'b0}};
    else if (spi_divider_sel && wb_we_i && !tip)
      begin
      `ifdef SPI_DIVIDER_LEN_8
        if (wb_sel_i[0])
          divider <= wb_dat_i[`SPI_DIVIDER_LEN-1:0];
      `endif
      `ifdef SPI_DIVIDER_LEN_16
        if (wb_sel_i[0])
          divider[7:0] <= wb_dat_i[7:0];
        if (wb_sel_i[1])
          divider[`SPI_DIVIDER_LEN-1:8] <= wb_dat_i[`SPI_DIVIDER_LEN-1:8];
      `endif
      `ifdef SPI_DIVIDER_LEN_24
        if (wb_sel_i[0])
          divider[7:0] <= wb_dat_i[7:0];
        if (wb_sel_i[1])
          divider[15:8] <= wb_dat_i[15:8];
        if (wb_sel_i[2])
          divider[`SPI_DIVIDER_LEN-1:16] <= wb_dat_i[`SPI_DIVIDER_LEN-1:16];
      `endif
      `ifdef SPI_DIVIDER_LEN_32
        if (wb_sel_i[0])
          divider[7:0] <= wb_dat_i[7:0];
        if (wb_sel_i[1])
          divider[15:8] <= wb_dat_i[15:8];
        if (wb_sel_i[2])
          divider[23:16] <= wb_dat_i[23:16];
        if (wb_sel_i[3])
          divider[`SPI_DIVIDER_LEN-1:24] <= wb_dat_i[`SPI_DIVIDER_LEN-1:24];
      `endif
      end
  end
  
  // Ctrl register
  always @(posedge wb_clk_i)
  begin
    if (wb_rst_i)
      ctrl <= {`SPI_CTRL_BIT_NB{1'b0}};
    else if(spi_ctrl_sel && wb_we_i && !tip)
      begin
        if (wb_sel_i[0])
          ctrl[7:0] <= wb_dat_i[7:0] | {7'b0, ctrl[0]};
        if (wb_sel_i[1])
          ctrl[`SPI_CTRL_BIT_NB-1:8] <= wb_dat_i[`SPI_CTRL_BIT_NB-1:8];
      end
    else if(tip && last_bit && pos_edge)
      ctrl[`SPI_CTRL_GO] <= 1'b0;
  end
  
  assign rx_negedge = ctrl[`SPI_CTRL_RX_NEGEDGE];
  assign tx_negedge = ctrl[`SPI_CTRL_TX_NEGEDGE];
  assign go         = ctrl[`SPI_CTRL_GO];
  assign char_len   = ctrl[`SPI_CTRL_CHAR_LEN];
  assign lsb        = ctrl[`SPI_CTRL_LSB];
  assign ie         = ctrl[`SPI_CTRL_IE];
  assign ass        = ctrl[`SPI_CTRL_ASS];
  
  // Slave select register
  always @(posedge wb_clk_i)
  begin
    if (wb_rst_i)
      ss <= {`SPI_SS_NB{1'b0}};
    else if(spi_ss_sel && wb_we_i && !tip)
      begin
      `ifdef SPI_SS_NB_8
        if (wb_sel_i[0])
          ss <= wb_dat_i[`SPI_SS_NB-1:0];
      `endif
      `ifdef SPI_SS_NB_16
        if (wb_sel_i[0])
          ss[7:0] <= wb_dat_i[7:0];
        if (wb_sel_i[1])
          ss[`SPI_SS_NB-1:8] <= wb_dat_i[`SPI_SS_NB-1:8];
      `endif
      `ifdef SPI_SS_NB_24
        if (wb_sel_i[0])
          ss[7:0] <= wb_dat_i[7:0];
        if (wb_sel_i[1])
          ss[15:8] <= wb_dat_i[15:8];
        if (wb_sel_i[2])
          ss[`SPI_SS_NB-1:16] <= wb_dat_i[`SPI_SS_NB-1:16];
      `endif
      `ifdef SPI_SS_NB_32
        if (wb_sel_i[0])
          ss[7:0] <= wb_dat_i[7:0];
        if (wb_sel_i[1])
          ss[15:8] <= wb_dat_i[15:8];
        if (wb_sel_i[2])
          ss[23:16] <= wb_dat_i[23:16];
        if (wb_sel_i[3])
          ss[`SPI_SS_NB-1:24] <= wb_dat_i[`SPI_SS_NB-1:24];
      `endif
      end
  end
  
  assign ss_pad_o = ~((ss & {`SPI_SS_NB{tip & ass}}) | (ss & {`SPI_SS_NB{!ass}}));
  
  spi_clgen clgen (.clk_in(wb_clk_i), .rst(wb_rst_i), .go(go), .enable(tip), .last_clk(last_bit),
                   .divider(divider), .clk_out(sclk_pad_o), .pos_edge(pos_edge), 
                   .neg_edge(neg_edge));
  
  spi_shift shift (.clk(wb_clk_i), .rst(wb_rst_i), .len(char_len[`SPI_CHAR_LEN_BITS-1:0]),
                   .latch(spi_tx_sel[3:0] & {4{wb_we_i}}), .byte_sel(wb_sel_i), .lsb(lsb), 
                   .go(go), .pos_edge(pos_edge), .neg_edge(neg_edge), 
                   .rx_negedge(rx_negedge), .tx_negedge(tx_negedge),
                   .tip(tip), .last(last_bit), 
                   .p_in(wb_dat_i), .p_out(rx), 
                   .s_clk(sclk_pad_o), .s_in(miso_pad_i), .s_out(mosi_pad_o));
endmodule