CMOS crystal controlled oscillator

Claim 1

A CMOS crystal controlled oscillator for use in a semiconductor device having an internal data bus comprising: (a) a CMOS inverter composed of P and N type MOS FETs which are connected in series with each other; (b) a crystal element connected between signal input and output nodes of said CMOS inverter; (c) a first capacitor connected between said signal input node of said CMOS inverter and a ground potential; (d) a second capacitor connected between said signal output node of said CMOS inverter and said ground potential; (e) a feedback resistor connected between the signal input and output nodes of said CMOS inverter for providing a DC bias potential to said CMOS inverter; (f) a first current-limiting circuit connected between the P type MOS FET of said CMOS inverter and a power source potential for limiting a current through said CMOS inverter; said first current-limiting circuit comprising a plurality of P type MOS FETs which are connected in parallel; (g) a second current-limiting circuit connected between said N type MOS FET of said CMOS inverter and said ground potential for limiting a current flowing through said CMOS inverter; said second current-limiting circuit comprising a plurality of N type MOS FETs which are connected in parallel; and (h) a control register for controlling said first and second current-limiting circuits based on data on said internal data bus to reduce power consumption of said crystal control oscillator; wherein said plurality of P type MOS FETs are controlled selectively in response to data from said control register and wherein said plurality of N type MOS FETs are controlled selectively in response to data from said control register.