Programmable crystal oscillator

A programmable timing circuit comprising:

• a crystal;
• an oscillator circuit coupled to excite said crystal into generating a source frequency;
• a capacitive load circuit coupled to said crystal and configured to be programmable to a desired load capacitance, such as to selectively adjust said source frequency;
• and
• a phase locked loop circuit coupled said oscillator circuit, said phase locked loop circuit generating an output frequency as a product of said adjusted source frequency and a multiplication factor.

A programmable crystal oscillator, comprising:

• a crystal having an associated source frequency;
• an oscillator circuit;
• input lines coupling said crystal to said oscillator circuit;
• a programmable capacitive load, coupled to said input lines, for adjusting said source frequency according to a loading parameter;
• a phase locked loop circuit coupled to receive said adjusted source frequency and to generate a loop frequency in response thereto, said phase locked loop circuit multiplying said loop frequency by a frequency parameter to generate a desired output a frequency;
• and
• a programming circuit coupled to said programmable capacitive load circuit and to said phase locked loop circuit, said programming circuit storing said loading and frequency parameters for respectively programming said capacitive load circuit and said phase locked loop circuit.