Zero to main(): How to Write a Bootloader from Scratch | Interrupt

[francois]

@ForzaSanto

Question: I see in your post that the bootloader jumps to the application by calling the reset handler of the application and then it is the responsibility of the application reset handler to update the VTOR register. In other replies to this post it seems that some solutions update the VTOR register prior to jumping to the application. Is there a reason to do it one way or the other? Does the VTOR register not get cleared upon reset?

You are correct that’s a chip reset would clear VTOR, but calling the Reset_Handler of the application does not cause the chip to reset! In other words, when you go from bootloader to app, VTOR does not change unless you explicitly set it.

Whether you set VTOR before jumping to the app (i.e. in the bootloader code), or after (i.e. in the app code) is really up to you.