NXP Semiconductors

UM12262

FRDM-IMX91 Board User Manual

2.5 Boot mode and boot device configuration

The i.MX 91 processor offers multiple boot configurations, selectable by SW1 on the FRDM-IMX91 board.

In addition, the i.MX 91 can download a program image from a USB connection when configured in serial

download mode. The four dedicated BOOT MODE pins are used to select the various boot modes.

Figure 7 shows the boot mode selection switch.

Figure 7.  Boot mode selection switch

Table 12 describes the SW1 values used in different boot modes.

SW1 [3:0]

BOOT_MODE[3:0]

Boot core

Boot device

0001

0001

Serial downloader (USB)

0010

0010

uSDHC1 8-bit eMMC 5.1

0011

0011

Cortex-A55

uSDHC2 4-bit SD3.0

Table 12. Boot mode settings

On the FRDM-IMX91 board, the default boot mode is from the eMMC device. The other boot device is the

microSD connector. Set SW1[3:0] as 0010 to choose uSDHC1 (eMMC) as boot device, set 0011 to choose

uSDHC2 (SD), and set 0001 to enter USB serial download.

Note: For more information about the boot modes and boot device configuration, see chapter "System Boot" in

the i.MX 91 Applications Processor Reference Manual.

Figure 8 shows the connection of SW1 and i.MX 91 boot mode signals.

UM12262

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User manual

Rev. 3.0 — 22 April 2025

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