DSB75 Development Support Board Rev. B1 Hardware Description
Confidential / Released
DSB75_hd_v12
Page 48 of 96
2008-08-26
3.10 SD Card Interface
The SD card interface provides a card reader for SD (Secure Digital) memory cards.
It has a smooth push-push mechanism with front cover retention for temper-resistant card
insertion. There are two contacts for card detection and write protect detection.
The SD card interface can be operated in three modes:
•
SD 4 bit mode
•
SD 1 bit mode
•
SPI bus mode
The supported operation mode depends on the type of GSM module and the selected
configuration (see subsections 3.10.1, 3.10.2 and 3.10.3). Each mode has to be set and
configured on the DSB75 by slide switches.
Figure 25 shows the simplified interface schematic.
Figure 26 shows the location of card reader pins and slide switches.
Electrical characteristics are specified in section 8.
SD_CMD_I
SD_D0_I
SD_D1_I
SD_D2_I
SD_D3_I
8
7
6
5
4
3
2
1
9
DAT1
DAT0
GND
CLK
VDD
GND
CMD
CD/DAT3
DAT2
write
protect
slide
card
detect
SD card holder
SD Card
50k
2)
2) Internal switch is closed after power up and open
during regular data transfer, used for card detection,
if GPIO8 not available for card detection.
3) Card detect switch is closed when card is inserted.
4) Write protect switch is closed when card is unlocked
or MMC is inserted.
47k
B2B
X100
SD_D3_I
SD_CMD_I
SD_CLK_I
SD_D0_I
3
1
1
3
SD_xx
ASC1 1)
SD_DET
SD_WP
6
8
71-74,10,9
53,51,31,29
alternative
S301,303,
S305,307
S450-455
8
7
6
5
4
3
2
1
9
11
10
X301
1) ASC1= TXD1, RXD1, RTS1, CTS1
3
1
S300,302
S304,306
N412
3)
4)
SD_CLK_I
un
loc
k
lo
ck
VDD
6
4
Figure 25: SD card interface
