Product manual

Industrial Grade SD Card Interface Description
3-4 SanDisk Industrial Grade SD Product Manual, Rev. 1.0 © 2003 SANDISK CORPORATION
Figure 3-2 shows the bus topology of several cards with one host in SD Bus mode.
Figure 3-2. Industrial Grade SD Card System Bus Topology
During the initialization process, commands are sent to each card individually, allowing the application to detect the
cards and assign logical addresses to the physical slots. Data is always sent to each card individually. However, to
simplify the handling of the card stack, after initialization, all commands may be sent concurrently to all cards.
Addressing information is provided in the command packet.
The SD Bus allows dynamic configuration of the number of data lines. After power-up, by default, the Industrial
Grade SD Card will use only DAT0 for data transfer. After initialization, the host can change the bus width (number
of active data lines). This feature allows and easy trade off between hardware cost and system performance.
SD Memory
Card (A)
CLK
Vdd
Vss
D0-D3, CMD
SD Memory
Card (B)
CLK
Vdd
Vss
D0-D3, CMD
MultiMediaCard
(C)
CLK
Vdd
Vss
D0, CS, CMD
CLK
Vdd
Vss
D0-3(A),
CMD(A)
D0-3(B),
CMD(B)
D0-3(C)
CMD(C)
HOST
D1&D2 Not
Connected