ECE 274 - Digital Logic Lecture 22 Full-Custom Integrated Circuit
Full-Custom Integrated Circuit
Chip created specifically to implement the transistors of the desired chip Lecture 22 – Implementation Layout – detailed description how each transistor and wires should be Manufactured IC Technologies layed on a chips surface Typically use CAD tools to convert our circuit design to a custom layout
Fabricating an IC is often referred to a silicon spin
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Semicustom (Application Specific) Integrated Full-Custom Integrated Circuit Circuits - ASICs
Full-Custom Integrated Circuit Gate Arrays
Pros Utilize a chip whose transistors are pre-designed to forms rows (arrays) of logic gates on the chip Maximum performance Sometimes referred to as sea-of-gates Cons Pros High NRE (Non-Recurring Engineering) cost Much cheaper than full-custom IC Cost of setting of the fabrication of an IC Fabrications time is typically several weeks Often exceeds $1 million Cons May take months before first IC is available Less optimized compared to full-custom IC - Slower performance, bigger size, and more power consumption
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Semicustom (Application Specific) Integrated Semicustom (Application Specific) Integrated Circuits - ASICs Circuits - ASICs
Standard Cells Cell Array
Utilize library of pre-layed-out gates and smaller pieces of logic (cells) Standard cells are replaced on the IC with only the wiring left to be that a designer must instantiate and connect with wires completed Pros Sometimes referred to as sea of cells Can be better optimized than gate-array
Longer to design then gate-array Structured ASIC Cons Less optimized compared to full-custom IC Popular term describing ASICs whose gates or cells have been
Less NRE and fabrication time than full-custom IC preplaced
More expensive than gate-array
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Implementing Circuits Using only NAND Gates Implementing Circuits Using only NAND Gates
NAND gate is a universal gate Implementing an AND gate using a NAND gate
Universal gate – Logic gate that can implement any Boolean function using gates of that one type only
Implementing a NOT gate using a NAND gate
Implementing an OR gate using a NAND gate
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Semicustom (Application Specific) Integrated Circuits - ASICs Programmable ICs
Implementing Circuits Using only NAND Gates FPGAs – Field Programmable Gate Arrays
Implementing a half-adder using only NAND gates Prefabricated ICs that contain all of the transistors and wires
Designer can program the FPGA to implement our desried circuit
Programming refers to downloading a series of bits to the FPGA’s memory
Fast - Progamming typically takes seconds to minutes
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FPGAs – Field Programmable Gate Arrays Design Challenge
Lookup Tables Design Challenge
Memory used to implement a combinational circuit Draw a circuit using AND, OR and NOT gates for the function F(a,b,c) = N A 1-bit wide memory with N address lines (2 words) can implement a’bc + abc’. Convert that circuit into using NAND gates only. any Boolean combinational function of N variables
Due:
Next Lecture (Friday, December 2)
Extra Credit (Homework)
2 points
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