5. Boot Modes

5.1 Introduction

K3 supports booting from:

SPI NAND Flash
SPI NOR Flash
eMMC
UFS
SD/TF Card

5.2 Bootstrapping Pins

The boot process of K3 is controlled by a set of bootstrapping pins, which can be configured to determine the boot mode and other operating parameters. The definitions of the bootstrapping pins are listed below.

Pin Name	Bootstrapping Pin	Default Value
GPIO_65	STRAP[0]	0
GPIO_66	STRAP[1]	0
GPIO_68	STRAP[2]	0
GPIO_69	STRAP[3]	0
GPIO_64	STRAP[4]	0
GPIO_52	STRAP[5]	0

Details about the purpose of the different configurations of the bootstrapping pins are provided in the following subsections.

5.2.1 Boot Mode Selection

The boot mode is selected based on the state of the STRAP[0] and STRAP[1] pins, as shown below.

No.	STRAP[1]	STRAP[0]	Boot Mode
1	Down	Down	SD/TF Card → eMMC (default)
2	Up	Down	SD/TF Card → SPI NAND Flash
3	Down	Up	SD/TF Card → SPI NOR Flash
4	Up	Up	SD/TF Card → UFS

5.2.2 Download Mode Selection

The download mode is selected based on the state of the STRAP[2] pin, as shown below.

No.	STRAP[2]	Download Mode
1	Down	USB (default)
2	Up	UART

5.2.3 Boot Download Mode Selection

The boot download mode is selected based on the state of the STRAP[3] pin, as shown below.

No.	STRAP[3]	Boot Download Mode
1	Down	Boot mode as defined in Boot Mode Selection (default)
2	Up	Download mode as defined in Download Mode Selection

5.2.4 SPI NAND/NOR Flash Boot Voltage Selection

The boot voltage of SPI NAND/NOR Flash is selected based on the state of the STRAP[4] pin, as shown below.

No.	STRAP[4]	SPI NAND/NOR Flash Boot Voltage
1	Down	3.3V I/O
2	Up	1.8V I/O

5.2.5 DDR Type Selection

The DDR type is selected based on the state of the STRAP[5] pin, as shown below.

No.	STRAP[5]	DDR Type
1	Up	LPDDR4x
2	Down	LPDDR5

5.1 Introduction​

5.2 Bootstrapping Pins​

5.2.1 Boot Mode Selection​

5.2.2 Download Mode Selection​

5.2.3 Boot Download Mode Selection​

5.2.4 SPI NAND/NOR Flash Boot Voltage Selection​

5.2.5 DDR Type Selection​