Evolution of Logic Design and Its Abstractions

 Hello Dear Readers,

Today, I have summarized the evolution of logic design and two abstractions of the system design flow that has been discussed.

During the year 1958, Jack Kilby, a young electrical engineer at Texas Instrument figured out how to place the circuit elements, transistors, resistors, and capacitors, on a small piece of Germanium. But prior to the year 1958, many more revolutionized ideas were published and conceptualized.

Gottfried Leibniz was a famous mathematician and philosopher from Germany and he redefined the binary number system during the year 1676–1679. After the successful redefinition of number systems, the famous mathematician George Boole during the year 1854 invented the Boolean algebra and the revolution of the digital logic design set into motion. The actual invention of the prototype transistor model during the year 1946–1947 at Bell Labs by Shockley, Bardeen, Brattain had revolutionized the use of semiconductor in switching theory and for design of chip. The design of first working transistor was the biggest contribution by the Morris Tanenbaum during the year 1954 at Texas Instruments. The invention of CMOS logic during 1963 has made integration of logic cells very easy and it was predicted by Intel’s cofounder Gordon Moore that the density of the logic cells for the same silicon area will be doubled for every 18 to 24 months. This is what we call as Moore’s law. 

Fig.1:https://www.autodesk.com/products/eagle/blog/integrated-circuit-moores-law/

How Moore’s prediction was right, that experience engineers can get with the complex VLSI-based ASIC chip designs. In the present decade, the chip area has shrunk enough and process technology node on which design houses foundries are working is 14 nm and the chip has billions of cells of small silicon die size. With the evolutions in the design and manufacturing technologies; most of the designs are implemented by using Very High-Speed Integrated Circuit Hardware Description Language (VHSICHDL) or using Verilog. The evolution in the EDA industry has opened up new efficient path ways for the design engineers to complete the milestones in less time.

As shown in Fig.2 most of the designs have various abstraction levels. The design approach can be top-down or bottom-up. The implementation team takes decision about the right approach depending on the design complexity and availability of design resources. Most of the complex designs are using the top-down approach instead of bottom-up approach. The design is described as functional model initially and the architecture and micro-architecture of the design is described by understanding the functional design specifications. Architecture design involves the estimation of the memory processor logic and throughput with associative glue logic and functional design requirements. Architecture design is in the form of functional blocks and represents the functionality of design in the block diagram form. The micro-architecture is the detailed representation of every architecture block and it describes the block and sub block level details, interface and pin connections, and hierarchical design details. The information about synchronous or asynchronous designs and clock and reset trees can be also described in the micro-architecture document. RTL stands for Register Transfer Level. RTL design uses micro-architecture as reference design document and design can be coded using Verilog RTL for the required design functionality. The efficient design and coding guidelines at this stage plays important role and efficient RTL reduces the overall time requirement during the implementation phase. The outcome of RTL design is gate level netlist. Gate level netlist is the output from the RTL design stage after performing RTL synthesis and it is representation of the functional design in the form of combinational and sequential logic cells. Finally, the switch level design is the abstraction used at the layout to represent the design in the form of switches. PMOS, NMOS, and CMOS.

   Fig. 2: Vaibbhav Taraate (auth.) - Digital Logic Design Using Verilog_ Coding and RTL Synthesis

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