Subversion Repositories i2cgpio

// rtl program for i2c_gpio.v

`define         P0_P9_OP        4'b1010 //0x0A

//`define               P0_P3_OP        4'b1011 //0x0B

`define         P0_P3_OP        4'b0111 //0x07

`define         P4_P7_OP        4'b1110 //0xE0

//`define               P8_P9_OP        4'b1101 //0x0D

module i2c_gpio(clk, cs, sr_in, sda_out, sr_out, gpio);

   input clk,cs;

   input sr_in;

   output sda_out;

   output sr_out;

   output [7:0] gpio;

   reg [7:0]     sr;

   reg [7:0]     addrreg;

   reg          sda_out;

   reg          sr_out ;

   reg [7:0]     gpio;

   reg [7:0]     ram;

   wire [3:0]    addr;

   wire [3:0]    data;

   assign addr = sr[3:0];

   assign data = sr[7:4];

   always@(posedge clk)

     begin

        if (cs == 1'b0)

          begin

             sr_out <= sr[7];

             sr[7:1] <= sr[6:0];

             sr[0] <= sr_in;

          end

        begin

           if (addr[0] == 1'b0)               // low bit zero - start bit

             begin

                if(addr[3:0] == 4'h0E)         // 0xD is the address of the slave

                  begin

                     sda_out = 1'b1;          // high bit for Acknowledge to master

                     if(addr[3]== 1'b1)       // high bit for write

                       begin

                          case (addr[3:0])    // data[3:0] for data write

//                          `P0_P9_OP : gpio[7:4] <= {sr[0], sr[1], sr[2], sr[3], sr[4], sr[5], sr[6], sr[7]};

                            `P0_P3_OP : gpio[3:0] <= {data[0], data[1], data[2], data[3]};

                            `P4_P7_OP : gpio[3:0] <= {data[3], data[2], data[1], data[0]};

//                          `P8_P9_OP : gpio[9:8] <= {sr[0], sr[0]};

//                          default   : gpio[7:0] <= {sr[0], sr[0], sr[0], sr[0],

//                                                    sr[0], sr[0], sr[0], sr[0]};

                          endcase

                          sda_out = 1'b1;     // high bit for Acknowledge master

                       end

                     else

                       begin

                          sda_out = 1'bz;

                       end

                  end

             end

        end

     end

endmodule