The document discusses programmable logic arrays (PLAs), which are a type of programmable logic device (PLD) that contains an array of AND gates and OR gates. A PLA allows both the AND array and OR array to be programmed. It can implement combinational logic functions through a sum of products. The document compares PALs, PROMs, and PLAs, and provides details on the components and operation of a PLA, including examples of implementing logic functions with a PLA using K-maps and a programmable truth table. Advantages and disadvantages as well as applications of PLAs are described.

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)’

10. PLA Programmable Table

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