PAL Device Fundamentals — Pin/function makeup of a PAL16L8 Considering standard 20-pin PAL16L8 devices, which pin/function mix is correct for inputs and outputs?

Difficulty: Easy

Correct Answer: 10 inputs and 8 outputs.

Explanation:


Introduction / Context:
PAL (Programmable Array Logic) devices offered fixed OR planes with programmable AND arrays and configurable I/O macrocells. The PAL16L8 is a classic part number where “16” relates to the available product-term matrix width and “8” denotes eight outputs (often with active-LOW capability), making it a popular SPLD for glue logic.



Given Data / Assumptions:

  • Package: typically 20 pins (VCC and GND consume two pins).
  • Eight output macrocells are present (the “8”).
  • Remaining user pins are generally available as inputs.


Concept / Approach:
Subtract supply pins from the total, then account for eight output macrocells. The standard allocation yields ten input pins and eight output pins, with device-specific options for tri-state control or OE. Therefore, “10 inputs and 8 outputs” matches common PAL16L8 datasheets.



Step-by-Step Solution:
Total pins ≈ 20 → minus VCC and GND → 18 user pins.Eight are outputs (macrocell outputs).The remaining user pins serve as inputs (~10 inputs).Hence, PAL16L8 configuration: 10 inputs, 8 outputs.


Verification / Alternative check:
Legacy PAL/GAL datasheets list PAL16L8 as having 8 outputs and approximately 10 inputs, corroborating the standard understanding.


Why Other Options Are Wrong:

  • 8/8: Understates available inputs.
  • 16/16 or 16/8: Do not match the pin budget or the “16L8” part family behavior.


Common Pitfalls:
Interpreting “16” as the number of inputs; instead it aligns with internal product-term matrix resources rather than literal user I/O counts.


Final Answer:
10 inputs and 8 outputs.

More Questions from Programmable Logic Device

Discussion & Comments

No comments yet. Be the first to comment!
Join Discussion