|Re: HP Prime - usbtool.exe|
Message #7 Posted by fabrice48 on 10 Dec 2013, 2:35 p.m.,
in response to message #6 by Tim Wessman
In general situation like embeded electronic's :
the bootloader is a master piece of software whitch is able to write inside the ROM/FLASH where the firmware is.
The goal is to to replace the firmware if some condition are meeted
The bootloader can too rewrite itself.
Nowadays, microcontrolers own specific assembler instruction to write inside the entire flash memory during exe.
I said microcontroler, prime use microprocessor i guess, with external memory, in microcontroler the memory is inside the chip.
Bootloader is the fist executive part launched at start, generally his job is easy :
for example, if he see a communication line opened, he thought that a loader operation will probably be initiaded
The new firmware is received by an USB or serial port by the bootloader who rewrite the old and actual firmawre
In the other hand if during start operation, the bootloader did not see the load condition meeted he launch the real firmware, he call it and he stop to run.
so we can see generally see this in memory as two different field, the begining area is for the bootlaoder and the other is for the firmware.
if an error occur, during bootloader operation, there is no problem, you can retry the operation
BUT if this error is about the destruction of the bootloader, there is no easy recovery solutions, to be clear, a customer can't solve by himself, there is no issue
the user mus contact the developper to re-FLASH the bootlaoder, with a specific developpement probe, in the case of the prime the probe is an JTAG-PROBE.
Some microcontrolers can protect the bootloader area automaticly, so that this area can't be destroyed or rewrited, in this case the developper must indicate the address where the bootloader is to cover this entire area.