Why PLDs Displaced Many Fixed-Function ICs — Key advantages What explains the broad market adoption of PLDs relative to piles of fixed 74xx logic and discrete glue ICs?
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AOne PLD does the work of many ICs.
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BThe PLDs are cheaper.
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CLess power is required.
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DAll of the above
Answer
Correct Answer: All of the above
Explanation
Introduction / Context:Programmable Logic Devices (PLDs), including SPLDs, CPLDs, and FPGAs, became popular because they consolidate functionality, accelerate design cycles, and reduce bill-of-materials. Understanding these benefits clarifies why programmable solutions displaced many fixed-function ICs in modern designs.
Given Data / Assumptions:
- A single PLD can replace numerous SSI/MSI gates, counters, decoders, and glue logic.
- When considering total system cost (components, PCB area, assembly), PLDs can be cheaper.
- Lower quiescent power and reduced I/O toggling across many chips can decrease overall power.
Concept / Approach:Evaluate each proposed advantage at the system level. While a PLD may be more expensive than one small IC, it often replaces many, shrinking the PCB, reducing routing complexity, and lowering inventory. Power savings can result from fewer I/O drivers and shorter interconnects, especially in CPLDs/modern FPGAs with low-power modes.
Step-by-Step Solution:Function consolidation → fewer packages, simpler routing.Cost comparison → total BOM + assembly + engineering time can favor PLDs.Power analysis → fewer chip-to-chip transitions and modern low-power silicon reduce consumption.Thus, all listed advantages are valid in many real designs.
Verification / Alternative check:Case studies and app notes show PLD-based designs meeting cost, power, and schedule goals more effectively than equivalent boards stuffed with numerous SSI/MSI devices.
Why Other Options Are Wrong:
- Picking only a single benefit ignores the multi-dimensional advantages driving PLD adoption.
Common Pitfalls:Comparing a PLD to just one small IC on unit price without considering the full system trade space (board area, time-to-market, reprogrammability).
Final Answer:All of the above