درس مدارهای منطقی دانشگاه قم lc-qom.blogfa / Programmable Logic (PAL, PLA)

1. درس مدارهای منطقی دانشگاه قم http://lc-qom.blogfa.com/ Programmable Logic (PAL, PLA) تهیه شده توسط حسین امیرخانی مبتنی بر اسلایدهای درس مدارهای منطقی دانشگاه امیرکبیر http://ceit.aut.ac.ir/~szamani/index_files/logic.htm

2. Symbols for OR gate

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. Product Inputs Outputs t erm F F F F A B C 0 1 2 3 0 1 1 0 A B 1 1 - 0 0 0 1 B C - 0 1 0 1 0 0 A C 1 - 0 1 0 1 0 B C - 0 0 1 0 0 1 A 1 - - Design for PLA: Example • Implement the following functions using PLA Personality Matrix Input Side: 1 = asserted in term 0 = negated in term - = does not participate Output Side: 1 = term connected to output 0 = no connection to output

8. A C B AB B’C AC’ Product Inputs Outputs t erm F F F F A B C 0 1 2 3 0 1 1 0 B’C’ A B 1 1 - 0 0 0 1 B C - 0 1 A 0 1 0 0 A C 1 - 0 1 0 1 0 B C - 0 0 1 0 0 1 A 1 - - F1 F0 F3 F2 Design for PLA: Example Personality Matrix

9. Constants • Sometimes a PLA output must be programmed to be a constant 1 or a constant 0. • Manufacturer MAY pull upthe AND inputs: • P1 is always 1 is pulled UP or HIGH. • This constant 1 term drives the O1 output. • Manufacturer MAY pull downthe OR inputs: • O2 is 0. • Another 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 1st output section Only functions with at most four products can be implemented 2nd output section 3rd output section 4th output section

13. PAL x x x W = ABC + CD X = ABC + ACD + ACD + BCD Y = ACD + ACD + ABD

15. Final Remark A Programmable Logic achieves higher flexibility at the cost of lower speed!

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