Introduction to the SD Card
1-6
SanDisk Secure Digital (SD) Card Product Manual, Rev. 1.9 © 2003 SANDISK CORPORATION
1.5.9. SD Card—SD Bus Mode
The following sections provide valuable information on the SC Card in SD Bus mode.
1.5.9.1. SD Card Standard Compliance
The SD Card is fully compliant with SD Card Physical Layer Standard Specification V1.01. The structure of the
Card Specific Data (CSD) register is compliant with CSD Structure 1.0.
1.5.9.2. Negotiating Operation Conditions
The SD Card supports the operation condition verification sequence defined in the SD Card standard specifications.
Should the SD Card host define an operating voltage range, which is not supported by the SD Card it will put itself
in an inactive state and ignore any bus communication. The only way to get the card out of the inactive state is by
powering it down and up again.
In Addition the host can explicitly send the card to the inactive state by using the GO_INACTIVE_STATE
command.
1.5.9.3. Card Acquisition and Identification
The SD Card bus is a single master (SD Card host application) and multi-slaves (cards) bus. The Clock and Power
lines are common to all cards on the bus. During the identification process, the host accesses each card separately
through its own command lines. The SD Card’s CID register is pre-programmed with a unique card identification
number, which is used during the identification procedure.
In addition, the SD Card host can read the card’s CID register using the READ_CID SD Card command. The CID
register is programmed during the SD Card testing and formatting procedure, on the manufacturing floor. The SD
Card host can only read this register and not write to it.
An internal pull-up resistor on the DAT3 line may be used for card detection (insertion/removal). The resistor can
be disconnected during data transfer (using ACMD42). Additional practical card detection methods can be found in
SD Physical Specification’s Application Notes given by the SDA.
1.5.9.4. Card Status
The card status is separated into the following two fields:
•
Card Status
is stored in a 32-bit status register that is sent as the data field in the card respond to host
commands. Status register provides information about the card’s current state and completion codes
for the last host command. The card status can be explicitly read (polled) with the SEND_STATUS
command.
•
SD_Status
is stored in 512 bits that are sent as a single data block after it was requested by the host
using the SD_STATUS (ACMD13) command. SD_STATUS contains extended status bits that relate
to BUS_WIDTH, security related bits and future specific applications.