There are different types of "chips." there are ones that only can be programmed once and that's it. Others can be programmed multiples times.
Also in a chip that can be programmed multiple times, the code owner can decide to lock the chip so it can not be written any more.
Sometimes when the chip can be upgradable, USB is not the interface to do it. So if the USB port is not internally wired to "talk" to the chip they may use a serial port directly to some pins on the board.
This applies not only to vape gear.
Also in a chip that can be programmed multiple times, the code owner can decide to lock the chip so it can not be written any more.
Sometimes when the chip can be upgradable, USB is not the interface to do it. So if the USB port is not internally wired to "talk" to the chip they may use a serial port directly to some pins on the board.
This applies not only to vape gear.