Product manual

Industrial Grade SD Card Interface Description
SanDisk Industrial Grade SD Product Manual, Rev. 1.0 © 2003 SANDISK CORPORATION -3-7
3.4.1. Power-up
The power up of the Industrial Grade SD Card bus is handled locally in each card and the bus master.
Logic working level
Supply voltage
Supply ramp up time
Bus master sup ply voltage
ACMD
41
V
DD
max
Power up time
Initialization delay:
The maximum of
CMD2
N
CC
N
CC
N
CC
1 msec, 74 clock cycles
and supply ramp up time
Initialization sequence
V
DD
min
time
Time out value for initialization process = 1 sec
Optional repetitions of AMCD41
until no cards are responding
with busy bit set.
Valid voltage range
for commands CMD0,
15, 55, and ACMD41
Valid voltage
range for all
other commands
and memory
access.
ACMD
41
ACMD
41
Figure 3-5. Power-up Diagram
After power up, including hot insertion ( i.e., inserting a card when the bus is operating) the Industrial Grade SD
Card enters the idle state. During this state the card ignores all bus transactions until ACMD41 is received (ACMD
command type shall always precede with CMD55).
ACMD41 is a special synchronization command used to negotiate the operation voltage range and to poll the cards
until they are out of their power-up sequence. Besides the operation voltage profile of the cards, the response to
ACMD41 contains a busy flag, indicating that the card is still working on its power-up procedure and is not ready
for identification. This bit informs the host that the card is not ready. The host has to wait (and continue to poll the
cards, each one on his turn) until this bit is cleared. The maximum period of power up procedure of single card shall
not exceed 1 second.
Getting individual cards as well as the entire Industrial Grade SD Card system out of idle state is the responsibility
of the bus master. Because the power-up time and the supply ramp-up time depend on application parameters (such
as the maximum number of SD cards, the bus length, and the power supply unit), the host must ensure that the
power is built up to the operating level (the same level which will be specified in ACMD41) before ACMD41 is
transmitted.
After power up, the host starts the clock and sends the initialising 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.