Combination asynchronous cache system and automatic clock tuning device and method therefor

摘要

A combination asynchronous cache system and automatic clock tuning device is disclosed in which the automatic clock tuning device includes at least a pulse generator, a counter, a unit delay tree, a comparing device, and a feedback path. A portion of the feedback path delivers a signal of interest off of the device chip in order that the signal experience the effect of the actual system impedance prior to being returned to the device chip for further manipulation of the signal. A major concept of the automatic clock tuning device is to enable a cache data/tag Write Enable (WE) signal to be clocked off of the falling edge of a delayed version of the System Clock (SCLK). This Delayed Clock (DCLK) signal is automatically delayed by a pre-selected amount each time that the rising edge of the WE signal occurs earlier than the rising edge of the SCLK signal. As long as the rising edge of the WE signal occurs slightly before or at the same time as the rising edge of the SCLK signal the CPU address/data hold time is successfully accomplished without adding superfluous wait states.