Meaning
Defined byte addresses that mark the start and end of specific partitions within a non-volatile memory chip provide a roadmap for the system bootloader. These values separate the application code from the bootloader, the file system, the user partition and the calibration data. Accurate flash map offsets are necessary for ensuring that one segment of data does not overwrite another during a firmware update.
Offset Planning
Designing a memory layout involves balancing the size of the application against the space needed for backup images. If a device supports over-the-air updates, the flash map offsets must provide room for two copies of the firmware. One slot holds the active code while the second slot receives the new version.
This dual-slot configuration prevents the device from becoming unusable if a transfer is interrupted.
Firmware Migration
Changing the partition sizes in a later version of a product requires a careful transition. If the flash map offsets move, the bootloader must be updated to look at the new locations. Failing to manage this transition leads to a mismatch where the system attempts to execute data from the wrong address.
Storage Protection
Hardware locks or software logic often prevent writes to specific regions of the flash. By using flash map offsets to define a read-only zone for the bootloader, the system protects its most essential startup code from corruption. This boundary ensures that the device can always recover from a failed application update.
