OV7670读操作

//--------------------------------
//Funtion : sda_reg

always @(posedge clk or negedge rst_n)
begin
    if(!rst_n)
    begin
        iic_clk1 <= 1‘d1;
        sda_reg <= 1‘d1;
        riic_data <= 1‘d0;
    end
    else if(dir == 1‘b1)    //read
        case(time_cnt)
            //idle
            6‘d0 : begin
                        iic_clk1 <= 1‘d1;
                        sda_reg <= 1‘d1;  
                   end
            //start
            6‘d1 :begin
                        iic_clk1 <= 1‘d1;
                        sda_reg <= 1‘d0;
                  end
            6‘d2 :begin
                        iic_clk1 <= 1‘d0;
                        sda_reg <= 1‘d0;
                  end
                        
            //ID_addr
            6‘d3 :        sda_reg <= wdata_reg[23];
            6‘d4 :        sda_reg <= wdata_reg[22];
            6‘d5 :        sda_reg <= wdata_reg[21];
            6‘d6 :        sda_reg <= wdata_reg[20];
            6‘d7 :        sda_reg <= wdata_reg[19];
            6‘d8 :        sda_reg <= wdata_reg[18];
            6‘d9 :        sda_reg <= wdata_reg[17];
            6‘d10:        sda_reg <= wdata_reg[16];                
            //ack
            6‘d11:        iic_clk1<= 1‘d0;
            6‘d12:                       ;
            6‘d13:        iic_clk1<= 1‘d0;
            //sub_addr
            6‘d14:        sda_reg <= wdata_reg[15];
            6‘d15:        sda_reg <= wdata_reg[14];
            6‘d16:        sda_reg <= wdata_reg[13];
            6‘d17:        sda_reg <= wdata_reg[12];
            6‘d18:        sda_reg <= wdata_reg[11];
            6‘d19:        sda_reg <= wdata_reg[10];
            6‘d20:        sda_reg <= wdata_reg[9];
            6‘d21:        sda_reg <= wdata_reg[8];    
            //ack
            6‘d22:        iic_clk1<= 1‘d0;
            6‘d23:                       ;
            6‘d24:        iic_clk1<= 1‘d0;
            //stop
            6‘d25:begin
                        iic_clk1 <= 1‘d1;
                        sda_reg  <= 1‘d0;
                  end
            6‘d26:begin
                        iic_clk1 <= 1‘d1;
                        sda_reg  <= 1‘d1;
                  end
            //start
            6‘d27:begin
                        iic_clk1 <= 1‘d1;
                        sda_reg  <= 1‘d1;
                  end
            6‘d28:begin
                        iic_clk1 <= 1‘d1;
                        sda_reg  <= 1‘d0;
                  end
            //ID_addr
            6‘d29:        sda_reg <= wdata_reg[7];
            6‘d30:        sda_reg <= wdata_reg[6];
            6‘d31:        sda_reg <= wdata_reg[5];
            6‘d32:        sda_reg <= wdata_reg[4];
            6‘d33:        sda_reg <= wdata_reg[3];
            6‘d34:        sda_reg <= wdata_reg[2];
            6‘d35:        sda_reg <= wdata_reg[1];
            6‘d36:        sda_reg <= wdata_reg[0];    
            //ack
            6‘d37:        iic_clk1<= 1‘d0;
            6‘d38:                       ;
            6‘d39:        iic_clk1<= 1‘d0;
            //read_data
            6‘d40:        riic_data[7] <= iic_sda;
            6‘d41:        riic_data[6] <= iic_sda;
            6‘d42:        riic_data[5] <= iic_sda;
            6‘d43:        riic_data[4] <= iic_sda;
            6‘d44:        riic_data[3] <= iic_sda;
            6‘d45:        riic_data[2] <= iic_sda;
            6‘d46:        riic_data[1] <= iic_sda;
            6‘d47:        riic_data[0] <= iic_sda;
            //nack
            6‘d48:        sda_reg <= 1‘d1;
            //stop
            6‘d49:begin
                        iic_clk1 <= 1‘d1;
                        sda_reg  <= 1‘d0;
                  end
            6‘d50:begin
                        iic_clk1 <= 1‘d1;
                        sda_reg  <= 1‘d1;
                  end
            default :
                    begin
                        iic_clk1 <= 1‘d1;
                        sda_reg  <= 1‘d1;
                    end
        endcase     
end