Method for detecting the removal of a processing unit from a printed circuit board

摘要

Various methods for detecting the removal of a processing unit (10), such as a microprocessor or a microcontroller, from a printed circuit board (5) in a secure printing system, such as a postage metering system are provided. The methods utilize one or more of a real time clock (25) provided internal to the processing unit (10), a CMOS device provided on the printed circuit board (5) external to the processing unit, and CMOS memory internal to the processing unit (10) to detect the removal of the processing unit (10) and therefore an attack.