Crystal oscillator starting operation in an electricity meter

Abstract

Methods and apparatus for controlling operation of a low frequency oscillator upon reset of a microcomputer to achieve faster start-up time are described. In one aspect, the present invention is directed to a microcomputer having an oscillator input port, an oscillator output port, and an oscillator control port, and an oscillator coupled to the microcomputer oscillator output, input, and control ports. The microcomputer is programmed to control the output on the oscillator control port so that upon reset, the output transitions from a low state to a high state in accordance with a preselected frequency for a preselected period of time. More particularly, and in one exemplary embodiment, the microcomputer controls the output on the oscillator control port upon reset so that for a preselected cycle, the output is high for approximately about one-half cycle, low for approximately about one-half cycle, and then high for approximately about one-half cycle. Upon completion of such cycling, the microcomputer transitions the output on the control port to a high impedance state. Such control of the low frequency oscillator decreases the oscillator start-up time. Specifically, by generating the control signal having the desired frequency as described above, and then providing such control signal to the oscillator, the oscillator is 'kick started' to begin its operations more quickly than such operations would begin without such control signal.