Image Number 10 for United States Patent #8131789.
True random number generation circuitry utilizes a pair of oscillators driving a pair of linear feedback shift registers, with their output being combined to generate random numbers. At least one of the oscillators is programmable with a variable frequency. One embodiment controls the variable frequency of oscillators with output from one or more sets of oscillators and linear feedback shift registers. In other embodiments, linear feedback shift register output is captured and used to control the frequency of oscillators.