CPLD configuration memory — volatility characteristic A complex programmable logic device (CPLD) typically uses which type of on-chip configuration memory so that the user design is retained when power is removed?
-
Avolatile
-
Bnonvolatile
-
CEPROM
-
Dvolitile EPROM
-
Ebattery-backed SRAM only
Answer
Correct Answer: nonvolatile
Explanation
Introduction / Context:CPLDs and FPGAs differ notably in how they store configuration. Classic CPLDs employ nonvolatile technologies (EEPROM/flash/antifuse) that retain user logic without external configuration memory, enabling instant-on behavior and simplified system design compared to many SRAM-based FPGAs that require bitstream loading on power-up.
Given Data / Assumptions:
- CPLD families are commonly flash- or EEPROM-based.
- Nonvolatile storage retains configuration without power.
- Some modern FPGAs are SRAM-based and volatile (not the case for typical CPLDs).
Concept / Approach:Because CPLDs target glue logic and deterministic startup, nonvolatile configuration is preferred. The device powers up directly into the user-defined behavior with minimal latency and no need for an external configuration ROM or processor to load a bitstream.
Step-by-Step Reasoning:
Identify device class: CPLD.Recall typical storage: EEPROM/flash/antifuse → nonvolatile.Conclude that the correct characteristic is nonvolatile storage.Verification / Alternative check:Datasheets for common CPLD families (e.g., Xilinx CoolRunner, Intel/Altera MAX) state nonvolatile configuration using flash/EEPROM cells, confirming persistence across power cycles.
Why Other Options Are Wrong:
- volatile: describes SRAM-based architectures, more common in FPGAs.
- EPROM: a specific technology once used in PLDs; while nonvolatile, CPLDs typically use EEPROM/flash with electrical erase, not UV EPROM.
- “volitile EPROM”: misspelled and contradictory; EPROM is nonvolatile.
- battery-backed SRAM: not typical for CPLDs.
Common Pitfalls:
- Assuming all programmable logic behaves like SRAM-based FPGAs; CPLDs are different.
Final Answer:nonvolatile