Abstract: A phase lock loop circuit for a digital radio generates the sampling frequency for sampling an incoming signal by storing the samples of the incoming signal in an accumulator at a first frequency. The accumulator is unloaded at the sampling frequency. A microprocessor monitors the rate in which the samples are stored in the accumulator and provides a switching signal to vary the sampling frequency in small increments to prevent the accumulator from overflowing or underflowing.

Abstract: Proprietary information such as programs and/or data are protected using a secure processing system that includes a memory such as an EPROM in which the proprietary information is stored in a first portion of the memory. The stored information is encrypted by an encryption algorithm unique to the proprietor of the information. The stored information is assigned an unique key that will enable the information to be decrypted if the unique algorithm is known. A second portion of the memory has the unique key stored therein, the unique key is encrypted with a master encryption algorithm and can only be obtained by using a master key with the master algorithm. A processing unit such as a Digital Signal Processor (DSP) has both the proprietor's unique algorithm, master algorithm and master key available to it.