
User's Manual l MBa8MPxL UM 0100 l © 2022, TQ-Systems GmbH
Page 14
3.3.2
SD card interface
The MBa8MPxL offers a microSD card slot that can also be used as boot source. All signals are directly connected to the USDHC2
interface of the i.MX 8M Plus.
The TQMa8MPxL voltage V_3V3_SD supplies the microSD card slot. Since this voltage is controlled by SD_RESET#, the microSD
card is automatically reset in case of a Reset. An external switch is not required. Signal USDHC2_CD# has a pull-up on the
MBa8MPxL. All data lines are ESD protected.
Standard, High and Extended capacity card types are supported. Default Speed, High Speed, and SD UHS-1 Speed Mode SDR104
with theoretically max.104 MB/s are supported. UHS-1 Speed Modes SDR12, SDR25, SDR50 and DDR50 are theoretically
supported but not verified.
The TQMa8MPxL sets USDHC2 is to 1.8 V or 3.3 V automatically, depending on the transfer mode. The corresponding driver
handles the changeover; it does not have to be done explicitly.
USDHC2_WP is not used and is terminated accordingly.
TQMa8MPxL
SD Card Slot
USDHC2
3.3 V / 400 mA
V_3V3_SD
Figure 10: Block diagram SD card interface, MBa8MPxL
Table 9:
Pinout microSD card, X42
Pin
Pin name
Signal
Remark
1
DAT2
USDHC2_DATA2
10 kΩ PU
2
DAT3
USDHC2_DATA3
10 kΩ PU
3
CMD
USDHC2_CMD
10 kΩ PU
4
VDD
V_3V3_SD
Supply from TQMa8MPxL
5
CLK
USDHC2_CLK
–
6
GND
GND
–
7
DAT0
USDHC2_DATA0
10 kΩ PU
8
DAT1
USDHC2_DATA1
10 kΩ PU
SW1
CD#
GND
–
SW2
CD#
USDHC2_CD#
10 kΩ PU
M1…4
Shield
GND
–