Chapter 3 – SD Card Interface Description
Revision 2.2
SD Card Product Manual
© 2004 SanDisk Corporation
3-7
12/08/04
After power up, the host starts the clock and sends the initializing sequence on the CMD
line. This sequence is a contiguous stream of logical ‘1’s. The sequence length is the
maximum of 1msec, 74 clocks or the supply-ramp-up-time; the additional 10 clocks (over
the 64 clocks after what the card should be ready for communication) is provided to
eliminate power-up synchronization problems.
Every bus master shall have the capability to implement ACMD41 and CMD1. CMD1 will
be used to ask MultiMediaCards to send their operation conditions. In any case the
ACMD41 or the CMD1 shall be send separately to each card accessing it through its own
CMD line.
3.4.2
Bus Operating Conditions
SPI Mode bus operating conditions are identical to SD Card mode bus operating
conditions. Table 3-4 lists the power supply voltages. The CS (chip select) signal timing is
identical to the input signal timing (see Figure 3-8).
Table 3-4
Bus Operating Conditions Summary
Parameter Symbol
Min
Max
Unit
Remark
General
Peak voltage on all lines
---
-0.3
V
DD
+ 0.3
V
All Inputs
Input Leakage Current
---
-10
10
uA
All Outputs
Output Leakage Current
---
-10
10
uA
Power Supply Voltage
7
Supply Voltage
V
DD
2.0
3.6
V
CMD0, 15, 55,
ACMD41 commands
V
DD
2.7
3.6
V
Except CMD0, 15, 55,
ACMD41 commands
Supply voltage differentials
(V
SS1
, V
SS2
)
--- -0.3 0.3 V
Power-up Time
---
---
250
mS
From 0 V to V
DD
min.
3.4.3
Bus Signal Line Load
The total capacitance, C
L
, of the clock line in the SD Card bus is the sum of the bus-master
capacitance (C
HOST
), the bus capacitance (C
BUS
) itself and the capacitance (C
CARD
) of each
card connected to this line:
C
L
= C
HOST
+ C
BUS
+ N*C
CARD
Where
N
is the number of connected cards. Requiring the sum of the host and bus
capacitances not to exceed 30 pF for up to 10 cards, and 40 pF for up to 30 cards, the
values in Table 3-4 must not be exceeded.
7
The current consumption of any card during the power-up procedure must not exceed 10 mA.
