User's Manual l TQMa335xL UM 0101 l © 2019, TQ-Systems GmbH
Page 8
3.2.1.2
Boot modes
The AM335x provides a ROM with integrated boot loader.
After power-up the boot code initialises the hardware and then loads the program image from the selected boot device.
The integrated eMMC can be selected as standard boot device for the TQMa335xL.
More external boot devices are available as an alternative to eMMC.
Information thereto can be found in the AM335x Data Sheet (1) and the AM335x Reference Manual (3).
The AM335x supports so-called boot-sequences, i.e. if it fails to boot from the first boot device, it will try to boot from the next
one automatically.
Table 3:
Boot sequence
Boot Sequence
1
st
2
nd
3
rd
4
th
MMC0 / SD
SPI0 / NOR (not available on TQMa335xL)
UART0 / n.a.
USB0 / n.a.
MMC1/ eMMC
MMC0 / SD
UART0 / n.a.
USB0 / n.a.
SPI0 / NOR (not available on TQMa335xL)
MMC0 / SD
USB0 / n.a.
UART0 / n.a.
The boot device and its configuration as well as other AM335x settings have to be done via Boot Mode Register SYSBOOT.
The register SYSBOOT is read during reset from pins LCD_DATA[15:0].
Attention: Malfunction
On the carrier board must be ensured that even in the third and fourth boot sequence
no pins drive against each other!
The settings for other boot devices are to be taken from the AM335x Data Sheet (1).
