Programmable logic array (pla)
- 1. PROGRAMMABLE LOGIC ARRAY (PLA) DIGITAL LOGIC AND DESIGN BSCS 2ND (MA) GROUP 2
- 2. Programmable logic devices (PLD’s) •Special type of IC •Contains array of AND gates and OR gates •Programmable
- 3. Combinational PLD’s •A combinational PLD is an IC that provide an AND-OR sum of product implementation. •It has three types: •PROM (Programmable Read Only Memory) •PAL (Programmable Array Logic)
- 4. Comparison of PAL, PROM and PLA • PAL: Programmable AND array and fixed OR array. • PROM: Fixed And array which is construction as a decoder and programmable OR array. • PLA: Both the AND array and OR array can be programmed.
- 5. What is PLA? •It has both the AND arrays and OR arrays that can be programmed. •Block diagram of PLA:
- 6. Operators of PLA • Buffer: A buffer has only a single input and a single output with behavior that is the opposite of an NOT gate. It simply passes its input, unchanged, to its output.
- 7. CONTINUED… •AND gate: A HIGH output (1) results only if all the input to the AND gate are HIGH (1). •OR gate: A HIGH output (1) results if one or both the inputs to the gate are HIGH (1). •XOR gate: A HIGH output (1) results if (1) occurs only one time.
- 8. Implementation of PLA Question: F1(A, B, C)=∑(2,4,5,7) F2(A, B, C)= ∑(0,1,2,4,6)
- 9. Simplify using K-MAP F1=A’BC’+AC+AB’ F2=A’B’+C F1’=(ABC’+A’B’+AC’) F2’=(AC+BC)’
- 11. Circuit Diagram
- 12. ADVANTAGES OF PLA •Less time consuming •Easy to check and change •Adaptive to new technology
- 13. DISADVANTAGES OF PLA •Less speed •Larger chip area •Expensive
- 14. APPLICATIONS OF PLA •Micro-processor chip •Control logic •Code conversions •Micro-programmable code conversions •Decision tables •Bus priority resolvers •Memory overlay
- 15. Questions