Method and apparatus for data communication

摘要

A voltage regulation system for an automobile comprises a voltage regulator 16 and a powertrain control module 18. The powertrain control module 18 has a quartz crystal 26 as its time base, while the voltage regulator has a less-expensive, though more environmentally robust resistive-capacitive (RC) oscillator 22. The voltage regulator 16 and powertrain control module 18 communicate between one another using pulse-width modulation. Drift in the frequency of the RC oscillator 22 in the voltage regulator 16 is recognised through the powertrain control module's measurement of the frequency of the signal sent by the voltage regulator 16. The powertrain control module 18 adjusts the frequency of the signal it sends to the voltage regulator, assuring that the drift in frequency of the RC oscillator does not inhibit accurate PWM communications between the two devices. <IMAGE>