App note from Infineon on the basics of flash memories and their failure analysis recommendations. Link here (PDF)
Nonvolatile memory devices (like Flash) are often used in embedded applications that rely on the storage of system configuration, dynamic data, or both. This data needs to be retained during a power interrupt or power cycle. In case of a system malfunction, the reproducibility of the failure is influenced and depends on the state of the nonvolatile memory. This application note briefly explains the basic operation of Flash memory devices and recommends several analysis techniques.