Subversion Repositories openrisc_2011-10-31

/*

 *

 * Simple 8-bit wide GPIO module

 *

 * Can be made wider as needed, but must be done manually.

 *

 * First lot of bytes are the GPIO I/O regs

 * Second lot are the direction registers

 *

 * Set direction bit to '1' to output corresponding data bit.

 *

 * Register mapping:

 *

 * For 8 GPIOs we would have

 * adr 0: gpio data 7:0

 * adr 1: gpio dir 7:0

 *

 *

 * So for 24 GPIOs we would have

 * adr 0: gpio data 7:0

 * adr 1: gpio data 15:8

 * adr 2: gpio data 24:16

 * adr 3: gpio dir 7:0

 * adr 4: gpio dir 15:8

 * adr 5: gpio dir 24:16

 *

 * Obviously any width where width%8!=0 you must skip the remainder of the byte

 * before starting the dir registers.

 *

 * Backend pinout file needs to be updated for any GPIO width changes.

 *

 */

module gpio(

            wb_clk,

            wb_rst,

            wb_adr_i,

            wb_dat_i,

            wb_we_i,

            wb_cyc_i,

            wb_stb_i,

            wb_cti_i,

            wb_bte_i,

            wb_ack_o,

            wb_dat_o,

            wb_err_o,

            wb_rty_o,

            gpio_io);

   parameter gpio_io_width = 8;

   parameter gpio_dir_reset_val = 0;

   parameter gpio_o_reset_val = 0;

   parameter wb_dat_width = 8;

   parameter wb_adr_width = 3; // 8 bytes addressable

   input wb_clk;

   input wb_rst;

   input [wb_adr_width-1:0] wb_adr_i;

   input [wb_dat_width-1:0] wb_dat_i;

   input                    wb_we_i;

   input                    wb_cyc_i;

   input                    wb_stb_i;

   input [2:0]               wb_cti_i;

   input [1:0]               wb_bte_i;

   output reg [wb_dat_width-1:0] wb_dat_o; // constantly sampling gpio in bus

   output reg                wb_ack_o;

   output                    wb_err_o;

   output                    wb_rty_o;

   inout [gpio_io_width-1:0] gpio_io;

   // Internal registers

   reg [gpio_io_width-1:0]   gpio_dir;

   reg [gpio_io_width-1:0]   gpio_o;

   wire [gpio_io_width-1:0]  gpio_i;

   // Tristate logic for IO

   genvar                    i;

   generate

      for (i=0;i<gpio_io_width;i=i+1)  begin: gpio_tris

         assign gpio_io[i] = (gpio_dir[i]) ? gpio_o[i] : 1'bz;

         assign gpio_i[i] = (gpio_dir[i]) ? gpio_o[i] : gpio_io[i];

      end

   endgenerate

   // GPIO dir register

   always @(posedge wb_clk)

     if (wb_rst)

       gpio_dir <= 0; // All set to in at reset

     else if (wb_stb_i & wb_we_i)

       begin

          if (wb_adr_i == ((gpio_io_width/8)))

            gpio_dir[7:0] <= wb_dat_i;

/*

          if (wb_adr_i == ((gpio_io_width/8)+1))

            gpio_dir[15:8] <= wb_dat_i;

          if (wb_adr_i == ((gpio_io_width/8)+2))

            //gpio_dir[23:16] <= wb_dat_i;

            gpio_dir[21:16] <= wb_dat_i[5:0];

 */

          /* Add appropriate address detection here for wider GPIO */

       end

   // GPIO data out register

   always @(posedge wb_clk)

     if (wb_rst)

       gpio_o <= 0; // All set to in at reset

     else if (wb_stb_i & wb_we_i)

       begin

          if (wb_adr_i == 0)

            gpio_o[7:0] <= wb_dat_i;

/*

          if (wb_adr_i == 1)

            gpio_o[15:8] <= wb_dat_i;

          if (wb_adr_i == 2)

            gpio_o[23:16] <= wb_dat_i;

 */

          /* Add appropriate address detection here for wider GPIO */

       end

   // Register the gpio in signal

   always @(posedge wb_clk)

     begin

        // Data regs

        if (wb_adr_i == 0)

          wb_dat_o[7:0] <= gpio_i[7:0];

/*

        if (wb_adr_i == 1)

          wb_dat_o[7:0] <= gpio_i[15:8];

        if (wb_adr_i == 2)

          wb_dat_o[7:0] <= gpio_i[23:16];

*/

        /* Add appropriate address detection here for wider GPIO */

        // Direction regs

        if (wb_adr_i == 1)

          wb_dat_o[7:0] <= gpio_dir[7:0];

/*

        if (wb_adr_i == 4)

          wb_dat_o[7:0] <= gpio_dir[15:8];

        if (wb_adr_i == 5)

          wb_dat_o[7:0] <= gpio_dir[23:16];

*/

        /* Add appropriate address detection here for wider GPIO */

     end

   // Ack generation

   always @(posedge wb_clk)

     if (wb_rst)

       wb_ack_o <= 0;

     else if (wb_ack_o)

       wb_ack_o <= 0;

     else if (wb_stb_i & !wb_ack_o)

       wb_ack_o <= 1;

   assign wb_err_o = 0;

   assign wb_rty_o = 0;

endmodule // gpio