457
/
838
Nations Technologies Inc.
Tel
：
+86-755-86309900
：
Address: Nations Tower, #109 Baoshen Road, Hi-tech Park North.
Nanshan District, Shenzhen, 518057, P.R.China
all cards are initialized to a default relative card address (RCA=0x0001) and driven with a default clock frequency
of 400kHz (lowest speed, maximum current drive capability).
18.4.3
Card identification mode
After the host resets, it enters the card identification mode to search for a new card on the bus. In card identification
mode, the host resets all cards, verifies the operating voltage range, identifies the cards and asks each card for the
relative card address (RCA). This operation is done separately on each card's own command signal line CMD. All
data communication in card identification mode uses only the command line (CMD). During card identification, the
card should operate at clock rate F
OD
(400 kHz).
18.4.4
Card identification process
The identification process of different cards is different; for multimedia cards, the card identification process starts
with the clock frequency F
od
, and all SDIO_CMD outputs are driven open, allowing parallel connection of cards
during this process.
The identification process of the multimedia card is as follows:
1.
The bus is enabled
2.
The SDIO card host broadcasts the CMD1 (SEND_OP_COND) command, receives the operating conditions,
and obtains the "wire AND" of the contents of the operating condition registers of all cards
3.
If the card is not compatible, it will be placed in an inactive state
4.
The SDIO card host broadcasts a CMD2 command (ALL_SEND_CID) to all active cards. All active cards
simultaneously send their CID numbers serially. Those cards that detect that the output CID bits do not match
the data on the command line must Stop sending and wait for the next recognition cycle. In the end, only one
card can successfully transmit the complete CID to the SDIO card host and enter the identification state.
5.
The SDIO card host sends a CMD3 command (SET_RELATIVE_ADDR) to the card. This new address is called
the relative card address (RCA), which is shorter than the CID and is used to address the card. At this point, the
card goes into a standby state and no longer responds to the new identification process, and at the same time its
output drive changes from open circuit to push-pull mode.
6.
The SDIO card host repeats steps 4 and 5 above until a timeout condition is received.
The SD card identification process starts with the clock frequency F
od
, and all SDIO_CMD outputs are push-pull
drivers instead of open-circuit drivers. The identification process is as follows:
1.
The bus is enabled
2.
The SDIO card host broadcasts the ACMD41 (SEND_APP_OP_COND) command to get the contents of the
operating condition registers of all cards
3.
If the card is not compatible, it will be placed in an inactive state
4.
The SDIO card host broadcasts CMD2 (ALL_SEND_CID) to all activated cards, and all activated cards return
their unique card identification number (CID) and enter the identification state.
5.
The SDIO card host sends a CMD3 (SET_RELATIVE_ADDR) command and an address to an activated card,
