SDI Technologies SDIO Card User Manual
©Copyright 2000-2007 SD Card Association
SDIO Simplified Specification Version 2.00
5
An SDIO aware host sends CMD5 prior to the CMD55/ACMD41 pair, and thus would receive a valid OCR in the
R4 response to CMD5 and continue to initialize the card. Figure 3-2 shows the operation of an SDIO aware host
operating in the SD modes and Figure 3-3 shows the same operation for a host that operates in the SPI mode.
If the I/O portion of a card has received no CMD5, the I/O section remains inactive and shall not respond to any
command except CMD5. A combo card stays in the memory-only mode. If no memory is installed on the card
(i.e. an I/O only card in a non-SDIO aware host) the card would not respond to any memory command. This
satisfies the condition where a user uses some I/O function on the card such as Ethernet to load a music file to
the memory function of that card. The card is then removed and inserted into a non-SDIO aware host. That host
would not enable the I/O function (no CMD5) so would appear to the player as a memory-only card. If the host
were I/O aware, it would send the CMD5 to the card and the card would respond with R4. The host reads that R4
value and knows the number of available I/O functions and about the existence of any SD memory.
After the host has initialized the I/O portion of the card, it then reads the Common Information Area (CIA) of the
card (see 6.8). This is done by issuing a read command, starting with the byte at address 0x00, of I/O function 0.
The CIA contains the Card Common Control Registers (CCCR) and the Function Basic Registers (FBR). Also
included in the CIA are pointers to the card’s common Card Information Structure (CIS) and each individual
function’s CIS. The CIS structure is defined in section 16. The CIS includes information on power, function,
manufacturer and other things the host needs to determine if the I/O function(s) is appropriate to power-up. If the
host determines that the card should be activated, a register in the CCCR area enables the card and each
individual function. At this time, all functions of the I/O card are fully available. In addition, the host can control
the power consumption and enable/disable interrupts on a function-by-function basis. This access to I/O does
not interfere with memory access to the card if present.
Combo Cards can accept CMD15 with RCA=0000, as described in, but there is an exception for SD memory
only cards. Memory only cards require a non-zero RCA before the host may issue CMD15. Thus, CMD15 shall
be issued after CMD3 in the Standby state. In the case of ACMD41, it shall accept RCA=0x0000.
As shown in Figure 3-2 and Figure 3-3, an SDIO aware host shall send CMD5 arg=0 as part of the initialization
sequence after either Power On or a CMD 52 with write to I/O Reset. Sending CMD5 arg=0 that has not been
preceded by one of these two reset conditions shall not result in either the host or card entering the initialization
sequence.
R4 response to CMD5 and continue to initialize the card. Figure 3-2 shows the operation of an SDIO aware host
operating in the SD modes and Figure 3-3 shows the same operation for a host that operates in the SPI mode.
If the I/O portion of a card has received no CMD5, the I/O section remains inactive and shall not respond to any
command except CMD5. A combo card stays in the memory-only mode. If no memory is installed on the card
(i.e. an I/O only card in a non-SDIO aware host) the card would not respond to any memory command. This
satisfies the condition where a user uses some I/O function on the card such as Ethernet to load a music file to
the memory function of that card. The card is then removed and inserted into a non-SDIO aware host. That host
would not enable the I/O function (no CMD5) so would appear to the player as a memory-only card. If the host
were I/O aware, it would send the CMD5 to the card and the card would respond with R4. The host reads that R4
value and knows the number of available I/O functions and about the existence of any SD memory.
After the host has initialized the I/O portion of the card, it then reads the Common Information Area (CIA) of the
card (see 6.8). This is done by issuing a read command, starting with the byte at address 0x00, of I/O function 0.
The CIA contains the Card Common Control Registers (CCCR) and the Function Basic Registers (FBR). Also
included in the CIA are pointers to the card’s common Card Information Structure (CIS) and each individual
function’s CIS. The CIS structure is defined in section 16. The CIS includes information on power, function,
manufacturer and other things the host needs to determine if the I/O function(s) is appropriate to power-up. If the
host determines that the card should be activated, a register in the CCCR area enables the card and each
individual function. At this time, all functions of the I/O card are fully available. In addition, the host can control
the power consumption and enable/disable interrupts on a function-by-function basis. This access to I/O does
not interfere with memory access to the card if present.
Combo Cards can accept CMD15 with RCA=0000, as described in, but there is an exception for SD memory
only cards. Memory only cards require a non-zero RCA before the host may issue CMD15. Thus, CMD15 shall
be issued after CMD3 in the Standby state. In the case of ACMD41, it shall accept RCA=0x0000.
As shown in Figure 3-2 and Figure 3-3, an SDIO aware host shall send CMD5 arg=0 as part of the initialization
sequence after either Power On or a CMD 52 with write to I/O Reset. Sending CMD5 arg=0 that has not been
preceded by one of these two reset conditions shall not result in either the host or card entering the initialization
sequence.