How safe is flash memory?
Because flash memory does not have a physical write protection switch like RAM cards, some people have worried about the safety of data on it. A memory clear (ON-A-F) will not clear data stored in flash memory. In addition, there is no way for a user to clear flash memory without first sending four “special bytes” to the calculator from a computer. After all, if this were possible, the system software could be cleared at any time by a malicious person! It is IMPOSSIBLE to clear data in flash memory by accident, according to Jean-Yves Avenard. HP even tested sending 25,000 volts through the serial port and the flash memory survived. However, there have been some reports to the newsgroup describing cases where the flash has spontaneously erased user programs. This bug seems to have been fixed in ROM versions 1.14-3 and later.
