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Another SPI common characteristic, which is implemented in the miniSD Card as well, is byte transfers. All data

tokens are multiples of 8-bit bytes and always byte aligned to the CS signal. The SPI standard defines the physical

link only and not the complete data transfer protocol. In SPI Bus mode, the miniSD Card uses a subset of the

miniSD Card protocol and command set.

The miniSD Card identification and addressing algorithms are replaced by the hardware Chip Select (CS) signal. A

card (slave) is selected, for every command, by asserting (active low) the CS signal (see Figure 3-5). The CS signal

must be continuously active for the duration of the SPI transaction (command, response and data). The only

exception is card-programming time. At this time the host can de-assert the CS signal without affecting the

programming process.

The bi-directional CMD and DAT lines are replaced by unidirectional dataIn and dataOut signals. This eliminates

the ability of executing commands while data is being read or written. An exception is the multi read/write

operations. The Stop Transmission command can be sent during data read. In the multi block write operation a Stop

Transmission token is sent as the first byte of the data block.

Figure 3-5. miniSD Card Bus System

3.3.1. Power Protection

Same as SD Card mode.

SPI Bus Master

SPI Card SPI Card

Power Supply

SPI Bus (CLK, DataIn, DataOut)

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SanDisk SD032 Handbuch Seite 32