3 Selecting the Boot Mode

The block diagram that you are creating should also indicate which interface will be used for booting this device.

These devices contain an on-chip ROM Bootloader with the following features:

• The boot config pins are sampled at power-on-reset
• Sets up system for boot depending on boot configuration selected
• Depending on boot mode, copies image to internal RAM and then executes it
• Maximum size of the boot image is 128 KBytes

The following boot modes are supported:

• NOR Flash boot
• NAND Flash boot
• Serial Peripheral Interface (SPI) boot
• Secure Digital/Multimedia Card (SD/MMC) boot
• Ethernet Media Access Controller (EMAC) boot
• Universal Asynchronous Receiver/Transmitter (UART) boot
• Universal Serial Bus (USB) boot (like an ethernet card, not as mass storage)

If the first boot source fails to boot, the ROM will move on to the next one in the sequence. Keep in mind that some boot sources take some time to timeout if that boot source is not available.

To understand details on different boot modes, see the Initialization chapter in the AM335x Arm® Cortex™-A8 Microprocessors (MPUs) Technical Reference Manual.

Key Boot Considerations are:

• It is recommended to include population options for other boot modes to aid in development
• Boot pins have other functions after reset. Make sure your board design takes this into account when choosing pullup/down resistors for the boot pins.