Synthesized clock microcomputer with power saving

An energy efficient microcomputer system comprising:

• a microcomputer, including a central processing unit, having a plurality of predetermined clock pulse frequency requirements for the immediate execution of programmable tasks and including means for designating said requirements;
• a stable frequency source operative to produce timing pulses at a frequency which is less than the largest in magnitude of said plurality of predetermined clock pulse frequency requirements;
• and
• a frequency synthesizer coupled to said microcomputer and to said stable frequency source for generating and supplying synthesized clock pulses, said synthesizer including selecting means responsive to said designating means for selecting an output frequency of the synthesized clock pulses at frequencies equal to the magnitudes of said plurality of predetermined clock frequency requirements of said microcomputer;
• whereby the total power consumed by the elements of the microcomputer system are minimized when the said stable frequency source is operated at a frequency which is less than the largest of the predetermined clock pulse frequencies of the central processing unit and said microcomputer receives synthesized clock pulses from said frequency synthesizer at frequencies sufficient to satisfy the predetermined clock frequency requirements for the immediate execution of a programmable tasks.

For use in a microcomputer system, an energy efficient clock pulse frequency generator for a microcomputer having a plurality of predetermined clock pulse frequency requirements for the immediate execution of programmable tasks to maintain computational capability, comprising:

• a stable frequency source operative to produce timing pulses at a frequency which is less than the largest in magnitude of the plurality of predetermined clock pulse frequency requirements of the microcomputer;
• and
• a frequency synthesizer for coupling to the microcomputer, including means responsive to the clock pulse frequency requirement of the microcomputer, for selecting an output frequency of the synthesized clock pulses, said frequency synthesizer being coupled to said stable frequency source and generating and supplying synthesized clock pulses at frequencies equal in magnitude to the frequencies of said plurality of predetermined clock pulse frequency requirements of said microcomputer;
• whereby the operation of the stable frequency source at a frequency which is less than the largest in magnitude of the predetermined clock pulse frequency requirements and the operation of the synthesizer at frequencies equal to the clock pulse frequency requirements of the microcomputer results in power consumed by the clock pulse frequency source and frequency synthesizer being minimized while maintaining the computational capability of a microcomputer system.