GAL22V10 device pins (clarified) Which statement correctly summarizes the GAL22V10 pin configuration for user I/O and special pins?
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A10 output macrocells (I/O), 12 dedicated input pins, plus 2 special-purpose pins (CLK and OE)
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B10 outputs and 12 inputs only; there are no special-purpose pins
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C8 configurable I/O pins and 8 dedicated inputs
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D22 outputs and 10 inputs on a 24-pin package
Answer
Correct Answer: 10 output macrocells (I/O), 12 dedicated input pins, plus 2 special-purpose pins (CLK and OE)
Explanation
Introduction / Context:The GAL22V10 is a classic CMOS GAL (Generic Array Logic) device widely used for glue logic. Understanding its pinout is essential when replacing older PALs or migrating designs, because available inputs, I/Os, and special-purpose pins determine what logic can be packed into a single device.
Given Data / Assumptions:
- Package: 24 pins (typical DIP/PLCC/SOIC variants).
- Ten macrocells provide outputs with feedback (configurable features per macrocell).
- Dedicated inputs supply product terms into the AND array.
- Two special pins: a global clock and an output enable/control.
Concept / Approach:Device naming “22V10” hints at available resources: up to 22 inputs (including feedback) and 10 outputs (macrocells). Practically, pinout summaries list 10 I/O macrocells, 12 dedicated input pins, and 2 special function pins (often CLK and OE). These signals flow into the internal programmable AND array and fixed OR structure, with macrocells at the outputs for optional registering and tri-state control.
Step-by-Step Solution:
Identify macrocell count: 10 outputs that may feed back internally.Count dedicated inputs: 12 pins that only act as inputs.Account for special-purpose pins: 2 pins (typical roles are global CLK and OE).Confirm these add to 24 pins appropriate for the package family.Verification / Alternative check:Typical datasheets/tabular pin lists show 10 I/O macrocells and 12 inputs, plus CLK and OE or equivalent control pins, aligning with the correct option.
Why Other Options Are Wrong:
- No special pins: Contradicts the presence of global control pins.
- 8 configurable I/O: Confuses GAL22V10 with GAL16V8.
- 22 outputs and 10 inputs: Inverts the meaning of 22V10 and contradicts the physical pin count.
Common Pitfalls:Assuming all “22” pins are dedicated inputs (several are macrocell I/O) or overlooking feedback paths that let outputs act as inputs to logic.
Final Answer:10 output macrocells (I/O), 12 dedicated input pins, plus 2 special-purpose pins (CLK and OE)