Welcome to XDA

Search to go directly to your device's forum

Register an account

Unlock full posting privileges

Ask a question

No registration required
Post Reply

[Q] Bootloaders, JTAG and Serial Ports

OP jim5121111

8th February 2014, 09:07 PM   |  #1  
OP Junior Member
Thanks Meter: 0
 
1 posts
Join Date:Joined: Feb 2014
I have a general curiosity question. If the bootloader on a phone, such as a Galaxy S or S4, is not functioning properly, and the JTAG port nonfunctional, is there any other way to reprogram the bootloader, such as through a serial port? If not, can the chip be de-soldered and replaced? Is it a single chip that contains the CPU and the flash that contains the bootloader and android operating system, or are these on separate chips in general? Thanks.
10th February 2014, 05:10 AM   |  #2  
Renate NST's Avatar
Recognized Contributor / Recognized Developer
Boston
Thanks Meter: 822
 
2,000 posts
Join Date:Joined: Feb 2012
I have limited knowledge and can't generalize, but here's what I do know about one specific device.
That's the Nook Touch with a TI OMAP3621 processor.

The OMAP has ROM directly on chip for a very simple bootloader.
Depending on how the boot_sys pins are configured it can load from NAND, SD card, UART or USB.
It will load a primary bootloader (mlo, x-loader) which loads the secondary bootloader (u-boot.bin) which loads the kernel and ramdisk image(s).

Some devices do have a locked ROM bootloader which will only load signed primary bootloaders.
Post Reply Subscribe to Thread
Previous Thread Next Thread
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes