![]() ![]() Specific device tree blob (DTB) as an argument to U-Boot’s bootzĬommand that will extract and start the actual kernel. Image is typically performed through the use of scripts stored in the U-BootĮnvironment (all starting with the bootcmd ENV variable that getsĮxecuted after the autoboot countdown expires or manually by entering theīoot command at the U-Boot prompt). Operating system, kernel size, entry points, etc. This header includes the target architecture, the ZImage is the compressed kernel image wrapped with header info thatĭescribes the kernel. Program and manipulate a wide range of external memory devices as well asĪ helpful aid during custom board bringup. ![]() Viewed, modified, and saved using the env print, env set, andĮnv save commands, respectively. These environment variablesĪre stored in the uEnv.txt file on your storage medium or directly inĪ Flash-based memory if configured such. U-Boot environment variables can be configured. Parameters such as boot arguments and the kernel boot command. #U BOOT SPL SERIAL#U-Boot allows for powerful command-based control over the kernel bootĮnvironment via a serial terminal. Process for the next bootloader stage: U-Boot. The SPL has very limited configuration or user interaction,Īnd mainly serves to initialize the external DDR memory and set-up the boot The SPL is theįirst stage of U-Boot, and must be loaded from one of the boot sources into The second stage bootloader is known as the SPL (Secondary Program Loader),īut is sometimes referred to as the MLO (MMC Card Loader). Information on the SYSBOOT pins and associated boot parameters see the expected crystal frequency, bus width of external memory). These pins also set other boot parameters ![]() Second stage bootloader is configured by the voltage levels set on theĭevices SYSBOOT pins on startup. #U BOOT SPL CODE#The list of booting devices that the ROM code will search through for the Stage of bootloader (SPL) as well as loading the actual next stageīootloader code into memory and starting it
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