Posted on April 13, 2018 at 18:33The STM32L452 only has one flash bank. That means a mass erase will erase the entire flash memory. And it can't be used to erase part of that memory by write protecting a section of it (for example where a custom bootloader lives), because the RM says 'If the Flash memory contains a write-protected area (by WRP or PCROP), WRPERR is set
and the mass erase request is aborted.'So if FSTPG can only be used after a mass erase, and mass erase must erase every single word in the entire flash, then it seems this is a virtually useless 'feature'. Who in their right mind would build a commercial product that contains an MPU which is going to erase it's entire flash memory out in the field somewhere?
A large number of products being designed these days need the ability to be upgraded in the field. This is done by having some portion of the flash contain a custom bootloader, and some method of handing it a new application to be installed in the rest of flash. You never delete the bootloader. If an update failed at the time when the bootloader (and the rest of flash) was erased, the product becomes a brick. As long as the bootloader survives, then you can always try upgrading again and again. So no rational designer would create a bootloader that erases itself as part of the upgrade process.
If this mass erase requirement is really true, then I have lost a certain amount of respect for ST at this moment.
