Abstractions
CE-653 - Introduction and Fundamentals
20
}Combinational Logic Abstraction
}Treat transistor networks as digital switches to implement Boolean functions
}Pass-gate logic
}Restoring combinational logic
}Domino logic (DEC Alpha)
}Synchronous design abstraction
}Abstract time into ticks of a clock
}2-phase non-overlapping clocks w/ latches (Mead+Conway, 1979)
}Pulse-mode clocking with latches
}Single global clock with edge-triggered flip-flops
}Separates performance considerations from function (kind-of)
}
Use design patterns (discipline) to abstract away details of semiconductor devices and parasitics
Long-time tradition (from IBM) divides the design process into 1) architecture 2) implementation of the architecture by microarchitecture and 3) realization of the microarchitecture by physical design.  e.g., we design state-machines to control the busses in a microprocessor and then turn this into physical gates to finally realize the design.
This is an artificial distinction, much like the boundary between two countries.  Its just a line drawn for political purposes.  The issues of variance and increasing wiring delay and complexity mean this line is increasingly blurry.  We must consider the physical details at every stage--but to do so is timing consuming.

The common abstractions in present use should be familiar to you.
Shannon: equivalence of transistor networks and logic functions
2-phase non-overlapping clocks: can adjust clock-periods post-silicon to accommodate variation
Edge-Triggered flip-flop: implicit hold-time assumption