Boot Peripheral Options

Module boot configuration pins

The MitySOM-335x is capable of booting from a number of peripherals as defined by the state of the 16 LCD_DATA pins at the time of a reset. The state of the 16 data lines is sampled on the rising edge of the power-on-reset signal to determine the search order of peripherals for a valid boot image. The host board needs to provide pull up/down resistors (10K) on the lower 12 bits of the LCD_Data pins to select the desired boot mode for the target application. When a boot mode pin is being pulled up the resistor should utilize the VIO_3P3 voltage output from the MitySOM-335x module to ensure proper read timing. Please refer to the Appendix for a list of the pins that output this voltage net.

Note that bits 15 to 12 are already pulled high/low on the MitySOM-335x module as binary pattern 0100b.

Available Boot Options

Attached is the list of available boot peripherals for the AM335x processor. Note that this was pulled from the AM335x TRM (

Note that the SYSBOOT pins, 0 to 4, are responsible for determining the peripheral boot order. Please reference the TRM for further details. These are the first stage boot-loader restrictions. Note that once in UBoot based upon the pin-configuration you could load kernel and file system from any configured interface.

MMC1: eMMC/eSD/managed NAND memory device with 4GB capacity or greater (MMC port 1) - ****CANNOT USE AN SD CARD****
MMC0: MMC/SD Card/eMMC/eSD/managed NAND memory devices with less than 4GB capacity (MMC port 0)
NAND/NANDI2C: NAND flash memory/read geometry from EEPROM on I2C0
XIP: NOR or other XIP device without wait monitoring
XIP w/WAIT: NOR or other XIP device with wait monitoring
MUX1: Boot with XIP_MUX1 signals detailed in Table26-9
MUX2: Boot with XIP_MUX2 signals detailed in Table26-9
UART0: UART interface (UART port 0)
EMAC1: Ethernet interface (EMAC port 1)
USB0: USB interface (USB0)

Note that the onboard SPI EEPROM, if populated, is tied to SPI1 and therefore cannot be used as a direct boot device. A separate on-carrier-board SPI EEPROM would need to be placed for module boot if desired.

Note: The USB0 boot option creates a network RNDIS connection with a PC, it does not allow booting from a flash drive.

Example Boot Configurations

The following examples show the pull-up/down state of the boot configuration pins. Again pins 15 to 12 are fixed on the module as '0100'.

To boot from NAND:

11 to 5 4 to 0
0000111 10011

Boot order (from TRM): NAND, NANDI2C, MMC0, UART0

To boot from MMC:

11 to 5 4 to 0
1111111 10111

Boot order (from TRM): MMC0, SPI0, UART0, USB0

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