"And God made the two great lights; the greater light to rule the day, and the lesser light to rule the night: he made the stars also. And God set them in the firmament of heaven to give light upon the earth, and to rule over the day and over the night, and to divide the light from the darkness: and God saw that it was good" (Genesis 16 18).

This is history's first synchronous system run by a non-overlapping two-phase clock (the greater light to rule the day, and the lesser light to rule the night). In this system we are confronted for the first time with the problem of clock skew since the phases may overlap although the system has been built as immune to such clock skew.

This example should serve to illustrate how aspects of timing are crucial in nature and inherent to the very fact of existence. For this reason the analysis and study of these aspects is of decisive importance for understanding system behaviour. From the point of view of the design of electronic systems we should keep in mind that the functioning of a system is no more than a succession of events in the signals that run through the paths connecting the devices. Establishing an adequate succession of events, with respect to signal sequencing and the generation of adequate levels of voltage and current will determine the correct or incorrect functioning of the system.

According to Moore's Law, the number of transistors...