Re: CS302 GDB1 Solution and discussion

Total Marks 5
Starting Date Thursday, February 18, 2021
Closing Date Friday, February 19, 2021
Status Open
Question Title PAL vs PLA - Gaded Discussion Board (GDB)
Question Description

CS302 – Digital Logic Design

Graded Discussion Board

Suppose you had reduced a 32-variable Boolean expression using Quine–McCluskey algorithm to a 12-variable expression. For the generated simplified expression, you are required to implement it into a digital logic circuit. You can only use Programmable Array Logic (PAL) or Programmable Logic Array (PLA) devices.

Assume that we had selected a Programmable Array Logic (PAL) and a Programmable Logic Array (PLA) for you to choose between.

Using TICPAL22V10Z-25C (Programmable Array Logic)
Using PLUS173–10 (Programmable Logic Array).
Your selections among stated PLA and PAL must consider the following constraints:

Complexity
Flexibility
Speed
Functionality
Cost
Important instructions for GDB submission:

You must provide a precise and to the point answer. Your answer should be no more than 5 to 6 lines and do avoid irrelevant details.
Post your answer on the Graded Discussion Board (GDB), GDB through email or MDB will not be accepted in any case.
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Implementing a 12-variable Boolean expression derived from a complex 32-variable reduction requires a careful balance between architectural flexibility and hardware efficiency. Given the high number of inputs (12) and the likely high density of product terms (given it originated from 32 variables), the choice between the TICPAL22V10Z-25C and the PLUS173–10 is critical.

Comparison Analysis

Selection Criteria Based on Constraints

1. Complexity & Flexibility

The PLUS173–10 (PLA) is the superior choice here. Because your expression originated from a massive 32-variable space, the resulting 12-variable simplified version likely still contains many common product terms.

• The PAL has a fixed OR-plane, meaning if one output requires more product terms than the PAL’s hardware allows (usually 8–16 per output), the design fails.
• The PLA allows product term sharing. If multiple parts of your expression use the same logic, the PLA can reuse a single AND gate for multiple OR gates.

2. Speed

The TICPAL22V10Z-25C (PAL) wins on raw speed. Because the OR-plane is fixed (hardwired), the signal propagation delay () is significantly lower. If your digital circuit is part of a high-speed processor or timing-critical interface, the PAL’s 25ns rating (indicated by the “-25C”) is a predictable advantage.

3. Functionality

The TICPAL22V10Z-25C is a “22V10” architecture, meaning it has 12 inputs and 10 outputs with “Variable” product term distribution. This matches your 12-variable requirement perfectly. However, if the Quine–McCluskey reduction resulted in an expression with a high “sum-of-products” count that exceeds 10–16 terms for a single output, the PAL will physically not be able to compute the function.

4. Cost

Generally, PAL devices are more cost-effective for mass production and simpler logic because the manufacturing process for a single programmable plane is cheaper than a dual programmable plane.

Final Recommendation

Choose the PLUS173–10 (PLA).

Reasoning: While the PAL is faster, the complexity of a 12-variable expression reduced from 32 variables suggests a high likelihood of “product term heavy” logic. A PLA provides the necessary flexibility to map complex Boolean reductions without hitting the “fixed-OR” ceiling of a PAL. In a 32-to-12 variable reduction, logic density is usually a bigger bottleneck than nanosecond-level propagation speed.