Product manual

4.3.2. Operating Voltage Range Validation

The SD Physical Specification standard requires that all miniSD cards will be able to establish communication with

the host using any operating voltage between V

-min and

-max. However, during data transfer, minimum and

maximum values for

are defined in the operation condition register (OCR) and may not cover the whole range.

miniSD Card hosts are expected to read the card’s OCR register and select proper

values or reject the card.

SanDisk miniSD Cards that store the CID and CSD data in the payload memory can communicate this information

only under data-transfer V

conditions. This means if host and card have non-compatible

ranges, the card will

not be able to complete the identification cycle, nor to send CSD data.

SD_SEND_OP_COND (ACMD41) is designed to provide miniSD Card hosts with a mechanism to identify and

reject cards that do not match the host’s desired V

range. To accomplish this task, the host sends the required

voltage window as the operand of this command. SanDisk miniSD Cards that cannot perform data transfer in the

specified range must discard themselves from further bus operations and go into Inactive State. Note that ACMD41

is an application-specific command. Therefore, APP_CMD (CMD55) will always precede ACMD41. The RCA to

be used for CMD55 in idle_state will be the card’s default RCA = 0x0000.

The MultiMediaCard will not respond to ACMD41 (actually it will not respond to APP_CMD—CMD55, that

precedes it). The MultiMediaCard will be initialized as per the MultiMediaCard specification, using

SEND_OP_COND command (CMD1 of MultiMediaCard). The host should ignore an ILLEGAL_COMMAND

status in the MultiMediaCard response to CMD3, since it is a residue of ACMD41which is invalid in the

MultiMediaCard (CMD0, 1, 2 do not clear the status register). The host uses ACMD41 and CMD1 to distinguish

between MultiMediaCard and miniSD Cards in a system.

By omitting the voltage range in the command, the host can query each card and determine if there are any

incompatibilities before sending out-of-range cards into the Inactive State. This query should be used if the host can

select a common voltage range or wants to notify the application of non-usable cards in the stack.

The card can use the busy bit in the ACMD41 response to tell the host that it is still working on its power-up/reset

procedure (e.g., downloading the register information from memory field) and is not ready yet for communication.

In this case the host must repeat ACMD41 until the busy bit is cleared.

During the initialization procedure, the host is not allowed to change the OCR values. Changes in the OCR content

will be ignored by the miniSD Card. If there is a real change in the operating conditions, the host must reset the card

stack (using CMD0) and begin the initialization procedure once more. However, for accessing the cards already in

Inactive State, a hard reset must be done by switching the power supply off and on.

GO_INACTIVE_STATE (CMD15) can also be used to send an addressed miniSD Card into the Inactive State. This

command is used when the host explicitly wants to deactivate a card (e.g., host is changing V

into a range which

is known to be not supported by this card).