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User's Manual l TQMa6x & TQMa6xP UM 0403 l © 2019, TQ-Systems GmbH
Page 7
3.2.1.4
Boot modes
The i.MX6 contains a ROM with integrated boot loader.
After power-up, the boot code initializes the hardware and then loads the program image from the selected boot device.
The eMMC or the SPI NOR flash integrated on the TQMa6x can for example be selected as the standard boot device.
More boot interfaces are available as an alternative to booting from the integrated eMMC or the SPI NOR flash, see 3.2.1.6.
More information about boot interfaces and its configuration is to be taken from the i.MX6 data sheets (1), (2), and (3) as well as
the i.MX6 Reference Manuals (4), (5), and (6).
The boot device and its configuration, as well as different i.MX6 settings have to be set via different boot mode registers.
Therefore, the i.MX6 provides two possibilities:
•
Burning internal eFuses
•
Reading dedicated GPIO pins
The exact behaviour during booting depends on the value of the register BT_FUSE_SEL.
The following table shows the behaviour of the bit BT_FUSE_SEL in dependence of the selected boot mode.
Table 3:
Boot modes and BT_FUSE_SEL
BOOT_MODE[1:0]
Boot type
BT_FUSE_SEL
Usage
00
(default)
Boot from eFuses
BT_FUSE_SEL
= 0: Boot using Serial Loader (default)
BT_FUSE_SEL
= 1: Boot configuration is taken from eFuses
Series
01
Serial Downloader
n/a
Development
/ production
10
Internal Boot
BT_FUSE_SEL
= 0: Boot configuration is taken from BOOT_CFG pins (default)
BT_FUSE_SEL
= 1: Boot configuration is taken from eFuses
Development
11
Reserved
n/a
n/a
Attention: Malfunction
Burning an eFuse is irreversible!
TQ-Systems GmbH takes no responsibility for the correct operation of the TQMa6x,
if the user burns eFuses.
Attention: Boot configuration
It is recommended to implement a redundant update concept for field software updates
during the carrier board design.