Difficulty: Easy
Correct Answer: Correct
Explanation:
Introduction / Context: Complex Programmable Logic Devices (CPLDs) like the MAX7000S integrate macrocells and I/O elements (IOEs) with output-enable control. A common question is whether all user I/O pins provide tri-state capability for bus interfacing and high-impedance control.
Given Data / Assumptions:
Concept / Approach: A tri-state buffer allows an output to actively drive HIGH/LOW or present a high-impedance (Hi-Z) state under an output-enable (OE) control signal. For bus-based designs, Hi-Z is essential to prevent contention. In MAX7000S, user I/O pins incorporate OE-controlled tri-state drivers.
Step-by-Step Solution:
Identify I/O architecture: each IOE ties a macrocell to a pin with an OE path.Check behavior: when OE is deasserted, the output enters Hi-Z, making the pin effectively input/bidirectional.Therefore, general-purpose I/O pins offer tri-state output buffering.Verification / Alternative check:
Vendor handbooks show OE equations configurable per macrocell/pin, confirming Hi-Z control.Why Other Options Are Wrong:
Incorrect: Conflicts with standard CPLD I/O design.Only true on dedicated clock pins: Clocks are inputs; the statement concerns general I/O.Only true for input-only pins: Input-only pins do not “drive” at all; tri-state refers to output drivers.Common Pitfalls:
Counting VCC/GND/configuration pins as “I/O”.Confusing tri-state output capability with Schmitt-trigger input conditioning.Final Answer:
Correct
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