It's easy to corrupt a PDA device during a ROM update, especially if a power loss or software error occurs during the flash update. Most PDA vendors including PalmOne
release ROM updates on a regular basis. While they usually provide detailed instructions for the upgrade procedures, the chance of ROM corruption is a known risk.
PalmSource addresses this risk with increased security through a fault-tolerant Flash ROM update procedure. In the recently received US Patent
6,918,017, the company describes the procedure as such (see also attached drawings):
- The PDA contains two reset-resistent memory areas, whereas one (memory 1) is used to hold the actual Flash content that is normally used to startup the PDA, while the other (memory 2) is used for temporary storage;
- during a Flash upgrade the content of the new Flash is copied from your desktop to memory 2;
- upon the next reset, the device verifies the content in memory 2 and ensures that it is safe to load the information into memory 1;
- upon a positive verification, the content from memory 2 is copied to memory 1 and the device is resetted to load it with the new Flash content.