SDI Technologies SDIO Card manual Special Initialization considerations for Combo Cards

©Copyright 2000-2007 SD Card Association

SDIO Simplified Specification Version 2.00

Once an SDIO card has received a CMD5, the I/O portion of that card is enabled to respond normally to all further commands. This I/O enable of the functions within the I/O card shall remain set until a reset, power cycle or CMD52 with write to I/O reset is received by the card. Note that a SD memory only card may respond to a CMD5. The proper response for a memory only card would be Memory Present = 1 and Number of I/O Functions = 0. A memory only card built to SD Memory Card specification version 1.01 would detect the CMD5 as an illegal command and not respond. Note that unlike the similar memory command ACMD41, The SPI response to CMD5 does contain the OCR value from the card.

The I/O aware host sends CMD5. If the card responds with response R4 within the timeout value of Ncr as defined in the SD Physical Specification, the host determines the card’s configuration based on the data contained within the R4.

3.4Special Initialization considerations for Combo Cards

The host must be aware of some special situations when initializing a Combo card (SDIO plus SD Memory on the same card). This is caused because an implementation of the Combo card could actually use 2 separate controllers (Memory and I/O) in the same package and sharing the same bus lines. It important for the host to both detect and properly configure both parts (controllers) of a Combo card in order to prevent conflicts between the SDIO and the SD memory controller. These concerns are caused due to the different response to a reset (hard or soft) by the two controllers. Another concern is the value of the RCA (Relative Card Address) that exists within the Memory controller.

Note that this consideration is for the SD 1-bit and SD 4-bit modes only. In The SPI mode, card select/de-select is accomplished using the hardware CS line rather than the RCA.

3.4.1Re-initialize both I/O and Memory

When the host re-initializes both I/O and Memory controllers, it is strongly recommended that the host either execute a power reset (power off then on) or issues a reset commands to both controllers prior to any other operation. If the host chooses to use the reset commands, it shall issue CMD52 (I/O Reset) first, because it cannot issue CMD52 after CMD0 (see 4.4). After the reset, the host shall re-initialize both the I/O and Memory controller as defined in Figure 3-2.

3.4.2Using a Combo Card as SDIO only or SD Memory only after Combo Initialization

If a host intends to use only the SDIO or the Memory portion of a Combo Card, it is strongly recommended that the host power reset (power off then on) or issues reset commands to both controllers prior to any other operation. If the host chooses to use the reset commands, it shall issue CMD52 (I/O Reset) first, because it cannot issue CMD52 after CMD0 (see 4.4). After the resets, the host re-initializes either the I/O and Memory controller as defined in Figure 3-2.

3.4.3Acceptable Commands after Initialization

When the host re-initializes a Combo card, the acceptable commands that the host can issue are restricted until the I/O controller is placed into the command state and memory controller enters the transfer state. The kinds of prohibited commands are identified in the next section. Combo cards may not work correctly when the host issues these prohibited commands. The proper command sequence for the I/O controller and the memory controller are shown below. Note that CMD15 (GO_INACTIVE_STATE) can be sent at any time after initialization in order to send any addressed memory controller to the inactive state.

3.4.4Recommendations for RCA after Reset

Important Note: The RCA specification was not fully defined in SDIO Specification Ver1.0. There are two types of card (SDIO or Combo) with different responses to CMD0 or SDIO reset. The possible responses are:

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