rPi Bootloader

[last updated: 2019-10-25]
go to: rPi home page
-----

• These notes must be for a rPi-4 only, because both my otherwise-working-just-fine rPi-3's fail this test...
• To check that the bootloader is working correctly, turn off the power,
  unplug everything from the Raspberry Pi 4, including the SD card,
  and then turn the power back on.
• If the green LED blinks with a repeating pattern, then the bootloader is running correctly, and indicating that start*.elf has not been found.
• Any other actions imply that the bootloader is not working correctly and should be reinstalled using recovery.bin.
• from: (link to:) [here]
• Raspberry Pi boot process:
• When the Raspberry Pi is first turned on, the ARM core is off, and the GPU core is on. At this point the SDRAM is disabled.
• The GPU starts executing the first stage bootloader, which is stored in ROM on the SoC.
  The first stage bootloader reads the SD card, and loads the second stage bootloader (bootcode.bin) into the L2 cache, and runs it.
• bootcode.bin enables SDRAM, and reads the third stage bootloader (loader.bin) from the SD card into RAM, and runs it.
• loader.bin reads the GPU firmware (start.elf).

.

.

.

eof