Abstract: An integrated circuit (IC) having a clock switch that switches the system clock between an internal clock and an external clock based on whether or not the IC has finished downloading device configuration at boot and on whether or not the internal clock is functional. Further restrictions on the use of the external clock are imposed by the clock switch based on a life-cycle state of the IC. The use of the clock switch makes it significantly more difficult for the clock to be tampered with, thereby protecting the security settings of the IC and/or preventing unauthorized access to secure data stored on the IC using an external-clock-based security attack.

Abstract: An integrated circuit (IC) having a clock switch that switches the system clock between an internal clock and an external clock based on whether or not the IC has finished downloading device configuration at boot and on whether or not the internal clock is functional. Further restrictions on the use of the external clock are imposed by the clock switch based on a life-cycle state of the IC. The use of the clock switch makes it significantly more difficult for the clock to be tampered with, thereby protecting the security settings of the IC and/or preventing unauthorized access to secure data stored on the IC using an external-clock-based security attack.