477
/
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
2.
Broadcast Command with Response (BCR): sent to all cards and received responses from all cards at the same
time;
3.
Command (AC) with addressing (point-to-point): sent to the addressed card, there is no data transmission on the
SDIO_DAT signal line.
Data transfer command (AC) with addressing (point-to-point): sent to the addressed card, SDIO_DAT signal line for
data transfer.
18.5.4
Command format
The command format consists of command and response.
Command:
A command is used to start an operation. The host sends a command with an address or a broadcast
command to a specified card or all cards (the broadcast command is only applicable to MMC V3.31 or earlier
versions). All commands have a fixed length of 48 bits and are transmitted serially on the CMD line. The following
table gives the general command format on Multimedia Cards, SD Memory Cards and SDIO Cards
The CE-ATA command is an extension of the MMC V4.2 command, so it has the same format.
The command channel operates in half-duplex mode, so that commands and responses can be sent and received
separately. If the CPSM is not in the transmit state, the SDIO_CMD output is in a high-impedance state, as shown in
Figure 20-11 Bit sequence. Data on SDIO_CMD is synchronized with the rising edge of SDIO_CLK.
Table 18-22 Command format
Bit
Width
Value
Description
47
1
0
Start bit
46
1
1
Transmission bit
[45:40]
6
-
Command index
[39:8]
32
-
Parameter
[7:1]
7
-
CRC7
0
1
1
End bit
Response:
The response is a response to the previously received command, which is sent to the host by a card with
a specified address. For all cards of MMC V3.31 or earlier, the response is sent simultaneously; the response is
serially transmitted on the SDIO_CMD line.
SDIO supports two response types: 48-bit short response and 136-bit long response. Both types have CRC error
detection:
Note: If the response does not contain a CRC (such as the response to CMD1), the device driver SHOULD ignore
the CRC failure status.
Table 18-23
Short response format
Bit
Width
Value
Description
47
1
0
Start bit
46
1
0
Transmission bit
[45:40]
6
-
Command index