How does ST-LINK upgrade NUCLEO when bin files are saved into NUCLEO disc character?

[xww.17]

In this linked video,

https://www.youtube.com/watch?v=BrMw5TNQROo&feature=youtu.be

we can see that just by saving the bin file in the NUCLEO disc character, ST-LInk will automatically brush the program into NUCLEO, and then NUCLEO restarts to run the new program.

Can you explain to me the principle of STLINK upgrade in this process? Begin with the letter from saving bin files to NUCLEO. Thank you very much. If there are related documents, please give them to me. Thanks very much.

[xww.17]

[Tesla DeLorean]

The mechanics here are quite complicated, but it pretends to be a mass storage controller with a file system. It fakes the block requests presenting file system structures so that when the OS writes a file the blocks of data written are mapped to​ blocks of flash on the chip itself.