原创 FPGA读写2PORTRAM过程分析2

IDLE:

                                     begin

                                     //添加RESET状态

                                       data_wr<='h0;//写数据初始化

                                        ioRDY1_SLWRn<='b1;

                                        ioRDY0_SLRDn<='b1;         //USBFIFO 读

                                        oPA2_SLOEn<='b1;

                                        oPA4_FIFO0<='b1;

                                        oPA5_FIFO1<='b1;

//这里选择的是EP8，参考上面的图片，其实无所谓，待会还重新设置。

                                               oe<='b0;

                                               FFlagA<='b0;

                                               sram_d<='h0;

                                               data_wr<='h0;         

                                               sram_a_i<='h1fff;

                                               sram_a_o<='h1fff;

                                               sram_rden<='b0;

                                               sram_wren<='b0;

                                               wr_flag<='b0;

                                               datacnt<='h1fff;

                                               STATE<=READ_EVENT;

                                     End

进入下一个状态

READ_EVENT:                  //read from USB EP2

                                 begin

                                     wr_flag<='b1;

                                     oPA4_FIFO0<='b0;             

                                     oPA5_FIFO1<='b0;

                                     STATE<=POINT_TO_OUT_FIFO;

                                  End

POINT_TO_OUT_FIFO:        begin

                             if(ioCTL2_FLAGC)  //not empty 也就是有数据可以读取

                                    begin

                                          oPA2_SLOEn<='b0;

                                          ioRDY0_SLRDn<='b1;      

                                          STATE<=DATA_READY;

                                     end

                               else

                                    begin

                                       oPA2_SLOEn<='b1;

                                       ioRDY0_SLRDn<='b1;

                                       STATE<=POINT_TO_OUT_FIFO;

                                    end

                         end

然后进入数据准备好的状态

DATA_READY:  //write SRAM 这里指的是读取USBFIFO，然后把读到的数据写到SRAM里面

                             begin

                                  if(ioCTL2_FLAGC)  //not empty

                                          begin

                                              PA2_SLOEn<='b0;//最好也把这句加上吧

                                              ioRDY0_SLRDn<='b0;

                                              sram_a_i<=sram_a_i+1;                                     

                                              sram_d<=ioUSB_D;         

//这里是写数据到SRAM，所以SRAM地址使用了SRAM_A_I，在写之前加一，SRAM_WREN信号为1，使能写功能。        

                                              sram_wren<='b1;

                                              sram_rden<='b0;

                                              STATE<=READ;

                                          end

                                    else

                                          begin

                                              ioRDY0_SLRDn<='b1;

                                              oPA2_SLOEn<='b1;

                                              STATE<=POINT_TO_OUT_FIFO;

                                           end

                              end