Patent ID: 7659497

Claim:
A method of executing an electrical function on an integrated circuit chip, comprising the steps of: activating a photodiode in the chip through a spectrally selected external light activation, including the steps of charging the photodiode to a given voltage level, reducing the voltage level of the photodiode, and applying said external light to the photodiode to control the reduction of the voltage level of the photodiode; and using said activated photodiode to activate an electrical function on the chip, including the step of, when the voltage level of the photodiode falls below a defined level, using said voltage level to activate said electrical function; and wherein the charging step includes the step of applying a reset signal to the photodiode at a regular clock frequency thereby to recharge the photodiode to the given level at regular clock frequencies and whereby external light above a given illumination level is required to activate said electrical function.