User's Manual l TQMa8MxML UM 0103 l © 2022, TQ-Systems GmbH
Page 20
3.2.1.5
Boot Modes
The i.MX 8M Mini and i.MX 8M Nano CPUs boot in different ways. However, both have a ROM with integrated boot loader.
After the release of PMIC_POR# the System Controller (SCU) boots from the internal ROM and then loads the program image
from the selected boot device. For example, the integrated eMMC or the SPI NOR Flash can be selected as the default boot
device. The following boot sources are supported by TQMa8MxML and TQMa8MxNL:
•
eMMC
•
QSPI NOR
•
USB OTG
•
SD card
More information about the boot flow can be found in the Reference Manuals (1), (2), and the Data Sheets (3), (4)
of i.MX 8M Mini and i.MX 8M Nano. Alternatively, an image can be loaded into the internal RAM using the serial downloader.
3.2.1.6
Boot configuration i.MX 8M Mini
The i.MX 8M Mini uses two BOOT_MODE pins, which are available on the TQMa8MxML's LGA pads. These require pull-up or
pull-down wiring to 3.3 V and Ground. The pull-up voltage used must be stable before the release of IMX_POR.
It is strongly recommended to use V_3V3 as pull-up voltage to ensure a reliable boot behaviour.
The recommended settings of the config pins for the respective interface are
highlighted in blue
.
The exact boot behaviour depends on the BT_FUSE_SEL register value.
The following table shows the behaviour in dependence of BT_FUSE_SEL and selected Boot Mode:
Table 10:
Boot Modes i.MX 8M Mini
BOOT_MODE[1:0]
Boot type
BT_FUSE_SEL
Usage
00
(default)
Boot from eFuses
0: Boot using Serial Loader (default)
1: Boot Mode configuration is taken from eFuses
Series
01
Serial Downloader
Boot using Serial-Loader (USB OTG1)
Development / Testing
10
Internal Boot
0: Boot Mode configuration is taken from GPIOs (default)
1: Boot Mode configuration is taken from eFuses.
Development
11
(Reserved)
(n/a)
(n/a)
If Internal Boot is used, a detailed setting can be done with CFG Fuses. The CFG Fuses are multiplexed on the SAI1 interface pins
and require pull-up or pull-down resistors. With BOOT_CFG15 a general setting can be made independent of the boot device:
Table 11:
General boot configuration
Fuse
Signal
TQMa8MxML
Setting
BOOT_CFG15
SAI1_TXD7
P3
Infinite Loop (for debugging):
0:
Disabled
1:
Enabled
