ece15_13_2011_6 - Why Programmable Logic Facts It is most...

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1 ECE 15A Fundamentals of Logic Design Lecture 13 Malgorzata Marek-Sadowska Electrical and Computer Engineering Department UCSB 2 Why Programmable Logic? Facts: It is most economical to produce an IC in large volumes Many designs require only small volumes of ICs Need an IC that can be: Produced in large volumes Handle many designs required in small volumes A programmable logic part can be: made in large volumes programmed to implement large numbers of different low-volume designs 3 Programmable Logic - Additional Advantages Many programmable logic devices are field- programmable , i. e., can be programmed outside of the manufacturing environment Most programmable logic devices are erasable and reprogrammable . Allows “updating” a device or correction of errors Allows reuse the device for a different design Programmable logic devices can be used to prototype design that will be implemented for sale in regular ICs. Complete Intel Pentium designs were actually prototyped with specialized systems based on large numbers of VLSI programmable devices. 4 Gate Symbols . . . Conventional AND gate symbol ... Array Logic OR gate symbol a b c F F = abc ab c F = 0 F = ac 5 Programmable Array Logic (PAL) OR plane (array) is fixed, AND plane can be programmed # of product terms available per function (OR outputs) is limited 6 PAL - Sum of Products ABC AND plane Programmable AND array followed by fixed fan-in OR gates Programmable switch or fuse C B A B A f 2 C B A C B A f 1
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2 7 PAL Example inputs 1 st output section 2 nd output section 3 rd output section 4 th output section Only functions with at most four products can be implemented 8 PAL-based circuit implementation W = AB C + CD X = A BC + A CD + ACD + BCD Y = A D + ACD + A BD 9 Can we implement more complex functions using PALs?
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ece15_13_2011_6 - Why Programmable Logic Facts It is most...

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