ECE 274 - Digital Logic Lecture 22 Full-Custom

„ Full-Custom Integrated Circuit

„ Chip created specifically to implement the of the desired chip „ Lecture 22 – Implementation „ Layout – detailed description how each 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 – 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- 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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