SD Card

목차

SD 카드 역사

MMC 카드에서 유래

MMC: 1 bit mode 의 Data bus, Data 전송 최대지원 클럭 : 20MhzSD : Data bus 4 개 , 최대 지원 클럭 25Mhz (4*25Mhz = 100Mbps)

MMC 역시 4bit data Bus 와 전송클럭등의 성능을 높여 기능상의 우열비교하기 힘듬

SD 카드 종류

SD 구조

(Block diagram)

SD Card 인식 시 동작과정

  1. Card 삽입 시 Controller 는 Bus 상에서 Card 가 삽입 되었는지 확인 2. Controller 는 Card 삽입을 판단 CMD0 명령 전송 3. SD Card 는 CMD0 명령을 받고 S/W Reset 처리 4. Controller 는 CMD 8 명령 전송 이후 R7 응답이 있을 경우 CMD 2 와 CMD3 명령 전송

SD card Identification process

SD Memory Card Identification

2. When the Card detection Interrupt comes Bus driver is notified by callingSDHCDIndicateSlotStateChange(pHCContext, 0, DeviceInserted ); from HCD.

3. Then Bus Driver will start the Card Identificaction process for the Card present in the SD Slot by sending the sequence of commands to the HCD.

4. First command is CMD5 If the Response of this command is RSP_TIMEOUT that means the card present in the slot is the Memory card and if the respose is RSP_DONE then it is IO card.

5. So, Bus Driver sends further commands like CMD0, CMD1, ACMD41, CMD2, CMD3, CMD7, ACMD51, ACMD42, CMD6 to read the Internal registers present in the SD card and initialise the card thorough HCD.

6. At this point SD Bus driver loads the ClientDriver that is SDMemory.dll

7. Then this will be informed to the Storage Manager to mount this device.

8. Then FSD reads first sector present on the card thorough this stack and knows the File system, FAT32 and sector info also.

9. By successsively reading the volume info from the card it will enumerated in the File sytem.

10. You can see as "Storage Card" when you open the file explorer.

11. Finally, if you remove the card from the slot, card removal interrupt comes in the HCD's IST.

12. This need to be informed to the Bus Driver by calling SDHCDIndicateSlotStateChange(pHCContext, 0, DeviceEjected);

13. At this point Bus Driver mark's the slotstate as not ready so that no furhter command will be sent to the HCD. And Bus Driver unloads the SDMemory.dll

--------------------------------- | Clientdriver : SDMemory.dll --------------------------------- | BusDriver : SDBus.dll ------------------------------------------------- | Host Controller Driver (HCD): myhcd.dll <---Card detection IST runs here. ------------------------------------------------- | Host Controller Hardware. | -------------------------------------------------

stack of the drivers