Apparatus and method for automatically selecting an appropriate signal from a plurality of signals, based on the configuration of a peripheral installed within a computing device

Abstract

An improved computer clock circuit capable of automatically detecting the internal clock frequency of a peripheral component installed in a peripheral component interconnect (PCI) slot, and supplying the PCI slot with the a clock signal of a specified frequency. In one embodiment, the clock circuit comprises a reference clock generator having multiple clock frequencies, a phaselocked loop (PLL) based clock driver, and circuitry providing the clock driver with a selection signal indicative of the configuration of a component connected within a PCI slot. The PLL clock driver maintains phase coherency between the input and output signals, thereby reducing setup and hold times within the system and peripheral components. Additionally, the PLL clock driver reduces propagation delays within the clock circuitry, and greatly simplifies implementation of the clock circuit within a given design. In another embodiment of the invention, the clock driver is also used to generate clock signals having a predetermined relationship to those produced by the reference generator, in addition to the clock signal supplied to the PCI slot. A method of automatically selecting and providing a desired clock frequency to a PCI slot is also disclosed.