Understanding GAL devices in programmable logic Which statement correctly describes a Generic Array Logic (GAL) device in terms of programmability and technology?

Difficulty: Easy

Correct Answer: reprogrammable and a CMOS device

Explanation:


Introduction / Context:
Generic Array Logic devices were introduced to improve upon PALs by enabling reprogrammability. GALs became staples in digital design for glue logic, address decoding, and small state machines, particularly before CPLDs and FPGAs became ubiquitous.


Given Data / Assumptions:

  • GAL devices use nonvolatile memory cells (often EEPROM) for configuration.
  • They are implemented using CMOS technology for low power and high integration.
  • We consider standard commercial GALs from major vendors.


Concept / Approach:

Unlike earlier one-time programmable PALs that required windowed UV erasure or were blown fuses, GALs can be erased and reprogrammed electrically many times. Their CMOS implementation brings lower standby power and better noise margins compared with older bipolar families.


Step-by-Step Reasoning:

Identify programmability: GALs are reprogrammable via EEPROM cells.Identify technology: mainstream GALs are CMOS-based devices.Combine both traits → reprogrammable and a CMOS device.


Verification / Alternative check:

Look at datasheets for GAL16V8 or GAL22V10 devices. They explicitly mention CMOS technology and electrically erasable programmability, enabling many design cycles with a single chip during prototyping.


Why Other Options Are Wrong:

  • One-time programmable: describes many PALs, not GALs.
  • Reprogrammable only: incomplete, ignores CMOS implementation.
  • CMOS only: incomplete, ignores reprogrammability feature.
  • Bipolar and not reprogrammable: incorrect for GALs.


Common Pitfalls:

  • Confusing GALs with PALs or PEEL devices. Always check the erasure and technology notes.
  • Assuming GALs are functionally identical to CPLDs; GALs are simpler and smaller scale.


Final Answer:

reprogrammable and a CMOS device

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