User's Manual l MBa7x UM 0101 l © 2020, TQ-Systems GmbH
Page 55
4.3.5
Boot-Mode configuration
With the MBa7x all boot sources available for the TQMa7x can be used:
•
eMMC
•
QSPI Nor Flash
•
SD card
•
Serial Downloader via USB-OTG 1
Information about the boot configurations of the i.MX7 can be found in the TQMa7x User's Manual.
A High level at BOOT_EN# decouples the DIP switches S[1:4] from the LCD interface.
A Low level at BOOT_EN# connects the DIP switches S[1:4] to the LCD interface.
By default, BOOT_EN# is set to Low
the DIP switch circuit S[1:4] is connected to the LCD interface.
After the Boot Configuration is read out and the Boot Loader is started, the signals for the Boot Configuration BOOT_CFG[20:00]
are used as parallel LCD signals, depending on the multiplexing.
To prevent the LCD signals from being affected by the DIP switch circuitry after the boot process, they can be separated from
each other by IO buffers. The BOOT_EN# signal is available on a module GPIO for this purpose. After a reset, the buffers
automatically connect the DIP switch circuit.
DIP switch S2
TQMa7x
BOOT_MODE[1:0]
LCD_DATA[7:0]
LCD_DATA[15:8]
LCD_DATA[19:16]
DIP switch S3
DIP switch S4
DIP switch S1
Buffer
Buffer
Buffer
BOOT_CFG[19:16]
BOOT_CFG[15:8]
BOOT_CFG[7:0]
Header X23
LVDS Transceiver
LCD_DATA[23:20]
GPIO4_IO03
BOOT_EN#
Figure 46: Block diagram Boot Mode DIP switches S1 to S4
Note:
LCD interface, stubs
For EMC reasons and in order not to impair the signal quality, it is not recommended to connect the
LCD interface to a pin header and an LVDS transceiver.
On the MBa7x this was only implemented for functional Figure. In the final design, the LCD interface
should be connected as short as possible and without stubs to only one type of display.
