Power Protection; Electrical Interface - SanDisk SDSDB-32-201-80 - Industrial Grade Flash Memory Card Product Manual

SD Card Interface Description
Another SPI common characteristic, which is implemented in the SD 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 SD Card uses a subset of the SD Card
protocol and command set.
The SD Card identification and addressing algorithms are replaced by a hardware Chip Select (CS) signal. A card
(slave) is selected, for every command, by asserting (active low) the CS signal (see Figure 3-4). 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 uni-directional 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 3-4. SD Card Bus System

3.3.1. Power Protection

Same as for SD Card mode.

3.4. Electrical Interface

The following sections provide valuable information for the electrical interface.
3-6 SanDisk Secure Digital (SD) Card Product Manual, Rev. 1.9 © 2003 SANDISK CORPORATION