Method for generating a clock signal for universal asynchronous receiver transmitter by utilizing a pci-standardized clock signal

Abstract

A method is provided for use on a PCI-compliant (Peripheral Component Inter-connection) interface card having a UART (Universal Asynchronous Receiver-Transmitter) unit to generate a near-1.8432 MHz clock signal for clocking the UART unit. This method includes a first step of dividing a selected PCI clock signals, such as the 33 MHz PCI clock signal, from the PCI local bus by a predetermined integer frequency divisor; and a second step of multiplying the resulted frequency from the division by a predetermined integer frequency multiplier that allows the resulted frequency to be substantially close to 1.8432 MHz to serve as the intended clock signal to the UART unit. Preferably, the integer frequency multiplier is in the range equal to or greater than 8. This method can generate a more precise clock signal for the UART unit on the PCI-compliant interface card without having to use an external crystal oscillator. Moreover, the method requires only a frequency divider without a frequency multiplier to implement. The method allows the resulted frequency deviation to be smaller than the prior art and also allows a reduction in the implementation cost as compared to the prior art.