درس مدارهای منطقی دانشگاه قم Programmable Logic (PAL, PLA) تهیه شده توسط حسین امیرخانی مبتنی بر اسلایدهای درس مدارهای منطقی دانشگاه امیرکبیر
Symbols for OR gate 2
3 PLA (Programmable Logic Array)
4 PLA A 3×2 PLA with 4 product terms
5 PLA Pre-fabricated building block of many AND/OR gates (or NOR, NAND) General purpose logic building blocks “Personalized” or “customized” by making/ breaking connections among the gates This process is called “programming”
6 PLA Sums of Products
7 Design for PLA: Example Implement the following functions using PLA Personality Matrix 1 = asserted in term 0 = negated in term - = does not participate Input Side: 1 = term connected to output 0 = no connection to output Output Side: OutputsInputsProduct term A B C F F F F A B B C A C B C A
8 Personality Matrix OutputsInputsProduct term A B C F F F F A B B C A C B C A Design for PLA: Example
9 Constants Sometimes a PLA output must be programmed to be a constant 1 or a constant 0. Manufacturer MAY pull up the AND inputs: − P1 is always 1 is pulled UP or HIGH. − This constant 1 term drives the O1 output. Manufacturer MAY pull down the OR inputs: − O2 is 0. Anot her method of obtaining a constant-0 output is shown for O3.
10 PAL (Programmable Array Logic) Sums of Products but with a fixed OR array
11 PAL 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
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13 PAL W = ABC + CD X = ABC + ACD + ACD + BCD Y = ACD + ACD + ABD x x x
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Final Remark 15 A Programmable Logic achieves higher flexibility at the cost of lower speed!
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