Question 1

MAX7000 series overview (technology, scale, supply) Which statement best summarizes key characteristics available across the Altera MAX 7000 series?

Accepted Answer

Introduction / Context: The MAX7000 family (including S/A/AE variants) is a widely used CPLD line known for in-system programmability and EEPROM configuration. Recognizing its process technology, scaling across densities, and voltage options helps in selecting the right device for legacy and mixed-voltage designs. Given Data / Assumptions: MAX7000 devices use EEPROM (E2PROM) technology for nonvolatile configuration. The family spans multiple densities, reflected in a range of LAB counts. Different sub-families support various supply voltages, commonly from 5 V down to 3.3 V and 2.5 V offerings. Concept / Approach: Option (a) identifies the nonvolatile E2PROM configuration process. Option (b) summarizes the scalable architecture with a practical range of LAB counts used across members of the family. Option (c) reflects that the series includes variants supporting core/IO voltages across typical legacy (5 V) and modern (3.3/2.5 V) systems. Collectively, these statements are accurate for the broader MAX7000 line, making “all of the above” correct. Step-by-Step Solution: Check configuration tech: EEPROM/E2PROM → nonvolatile.Review density range: small to moderate devices → a few to many LABs (for example, single-digit to mid-teens).Confirm voltage variants: parts exist for 5 V, 3.3 V, and 2.5 V systems depending on subfamily.Therefore, select “all of the above.” Verification / Alternative check: Family summaries in vendor catalogs list E2PROM configuration, multiple density options (LAB counts), and supply options spanning 2.5–5 V across MAX7000 sub-lines. Why Other Options Are Wrong: Each single statement captures only part of the story; the comprehensive answer is “all of the above.” Common Pitfalls: Assuming every individual part in the family supports all voltages; voltage options vary by sub-family, so check the exact part number when designing power rails. Final Answer: all of the above

Question 2

JTAG-based test methods Which of the following test procedures specifically uses the IEEE 1149.1 JTAG standard?

Accepted Answer

Introduction / Context: JTAG (IEEE 1149.1) defines a standard interface and architecture for testing and debugging integrated circuits. Understanding which board-level test techniques rely on JTAG helps engineers plan for design-for-test (DFT), select connectors, and script automated tests in manufacturing. Given Data / Assumptions: Boundary-scan architecture inserts scan cells at I/O pins of compliant devices. The JTAG TAP (Test Access Port) provides standardized pins: TCK, TMS, TDI, TDO (and optionally TRST). EXTEST is a JTAG instruction used within the boundary-scan procedure. Concept / Approach: Among the options, “Boundary scan” is the board-level test methodology explicitly defined by IEEE 1149.1. It enables interconnect testing without physical probes by shifting test data into boundary cells and capturing responses. “EXTEST” is an instruction within boundary scan (not a procedure by itself). Bed-of-nails and flying-probe are physical probing methods, independent of JTAG, although they may be used in combination with JTAG on some lines. Step-by-Step Solution: Identify which option names a standardized JTAG method: Boundary scan.Recognize EXTEST as a JTAG instruction, not the overarching procedure.Exclude physical probing methods (bed-of-nails, flying probe) as non-JTAG by definition.Select “Boundary scan.” Verification / Alternative check: IEEE 1149.1 documentation describes boundary-scan test logic, instruction register, and opcodes (including EXTEST), confirming that boundary scan is the JTAG-based test methodology. Why Other Options Are Wrong: Bed-of-nails / Flying probe: Mechanical probing fixtures; not defined by the JTAG standard. EXTEST: A single JTAG instruction used during boundary-scan tests, not the procedure name. Common Pitfalls: Conflating a specific JTAG opcode (EXTEST) with the overall standardized method (boundary scan). Also, assuming physical ICT/FP testing equals JTAG testing—many boards use both but they are distinct techniques. Final Answer: Boundary scan

Question 3

Microprocessors and DSPs vs. general digital systems What is the defining difference that sets microprocessor/DSP-based systems apart from other digital systems?

Accepted Answer

Introduction / Context: Digital electronics spans a spectrum from fixed-function combinational/sequential logic to fully programmable computing cores. The key distinction for microprocessor and digital signal processor (DSP) systems is not merely speed or technology node, but the presence of a stored program that dictates behavior cycle by cycle. Given Data / Assumptions: A “microprocessor/DSP system” executes instructions fetched from memory. “Other digital systems” may be hardwired logic with no instruction stream. Performance (speed) is not the primary defining characteristic in this question. Concept / Approach: Microprocessors and DSPs are general-purpose or domain-focused compute engines. They read instructions (opcodes) and data from memory, execute them in sequence (possibly with branching), and thus their function can be changed by altering the program. By contrast, fixed digital logic implements behavior directly in gates and flip-flops; altering behavior requires modifying the hardware or configuration bits (in PLDs/FPGAs), not an instruction stream. Step-by-Step Solution: Identify the hallmark of a CPU/DSP: stored-program execution.Note that speed is incidental; many non-CPU digital ASICs can be faster.Therefore, the defining difference is the programmed sequence of instructions executed by the microprocessor/DSP.Map to options: the statement explicitly mentioning the microprocessor and a programmed sequence is correct. Verification / Alternative check: Consider reprogrammability: swapping firmware changes system behavior without changing hardware, which is unique to microprocessor/DSP architectures compared to fixed logic. Why Other Options Are Wrong: A: Many digital systems do not execute instructions; they are hardwired. C and D: Speed does not define the category; some fixed-function logic outruns general-purpose processors. Common Pitfalls: Equating “digital” with “programmable”; many digital devices are not instruction-driven. Final Answer: The microprocessor follows a programmed sequence of instructions that the designer specified.

Question 4

PAL architecture — path of product terms in combinational mode In a typical programmable array logic (PAL), each gate product term is ORed, and for combinational logic the resulting sum is then:

Accepted Answer

Introduction / Context: PAL devices use a programmable AND array followed by a fixed OR array. Understanding the signal path in combinational mode clarifies how polarity and buffering are handled before a logic signal reaches the output pin. Given Data / Assumptions: PAL: programmable AND array + fixed OR array. Combinational mode (no register stage). Output polarity and buffering are typically provided by an output inverter/buffer. Concept / Approach: Product terms are generated in the AND array. These terms are summed by the OR array to form the desired logic function. In standard PALs, the summed signal passes through an output buffer/inverter whose polarity may be programmable (via a “polarity fuse”). Thus, in combinational mode, the ORed signal does not go raw to the pin; it is routed through an inverter/buffer stage first. Step-by-Step Solution: Generate product terms in the AND plane.Sum selected products in the OR plane.Route sum to the output inverter/buffer for proper polarity and drive.Deliver final signal to the output pin. Verification / Alternative check: Check canonical PAL block diagrams: after the OR array, an inversion/polarity option is shown before the pad. Why Other Options Are Wrong: C: Skips the essential output buffer/inverter stage. D: Signal does not return to the AND plane after ORing. A: “Polarity fuse is restored” is not an operation step; polarity is configured, not dynamically restored. Common Pitfalls: Confusing PAL with PLA or GAL variants; while implementations differ, the output buffer/inverter remains standard in combinational mode. Final Answer: sent to an inverter for output

Question 5

CPLD composition — internal building blocks Within a complex programmable logic device (CPLD), the PAL-like simple PLD structures are organized into units commonly called:

Accepted Answer

Introduction / Context: CPLDs scale up the PAL/SPLD concept by combining multiple logic blocks with extensive interconnect. The terminology for these building blocks is essential when reading datasheets and fitting logic during synthesis. Given Data / Assumptions: CPLD = multiple logic blocks inside a single chip. Each block houses logic resources and registers. Vendors may vary names slightly, but “macrocell” is industry-standard. Concept / Approach: A macrocell typically contains the OR-summed product terms, an optional register (flip-flop), output enable control, and programmable polarity. Many macrocells aggregate into logic array blocks (LABs), which are then interconnected via a programmable routing matrix to form the full CPLD. Step-by-Step Solution: Recognize SPLD-like elements packaged into larger units.Identify industry term: “macrocell.”Recall that groups of macrocells form LABs or function blocks in vendor diagrams.Map to option list: macrocells is the correct designation. Verification / Alternative check: Vendor documentation (e.g., Altera/Intel MAX7000, Xilinx XC9500) consistently uses the term macrocell for the basic logic/register element. Why Other Options Are Wrong: Microcells: not standard nomenclature for CPLDs. AND/OR arrays and fuse-link arrays: these are structural components, not the encapsulated functional unit name. Common Pitfalls: Confusing macrocell vs. LAB naming; macrocells are the per-output logic units, LABs are groups of macrocells. Final Answer: macrocells

Question 6

GAL16V8 device modes — identifying supported operating modes Which of the following are valid operating modes for a GAL16V8 programmable logic device?

Accepted Answer

Introduction / Context: GAL (Generic Array Logic) devices, such as the GAL16V8, are pin-compatible, fuse-map compatible successors to classic PALs with reprogrammability. They offer multiple operating modes to trade off I/O usage, product term resources, and sequential capability. Given Data / Assumptions: GAL16V8 supports multiple personality modes. “Simple,” “Complex,” and “Registered” are common vendor-stated modes. Mode selection is determined by the design and fitter software. Concept / Approach: In Simple mode, outputs behave as straightforward combinational functions with abundant product term sharing. In Complex mode, macrocells offer richer control including output enable and more flexible product-term allocation. Registered mode dedicates macrocells to include flip-flops for synchronous designs, enabling counters and state machines directly in the device. Step-by-Step Solution: List vendor-documented modes: Simple, Complex, Registered.Recognize that each mode corresponds to a pin/function mapping template.Therefore, all listed modes are valid for a GAL16V8.Select “All of the above.” Verification / Alternative check: Reference a GAL16V8 datasheet or fitter options; the three modes appear explicitly. Why Other Options Are Wrong: Each single-mode choice is incomplete; the device supports more than one mode. Common Pitfalls: Assuming PAL-like fixed personalities; GALs add flexibility via reprogrammable logic and multiple modes. Final Answer: All of the above

Question 7

Programmable-logic expanders in SOP architectures: Evaluate the statement — “Expanders make it possible to increase the number of product terms available to a programmable sum-of-products (SOP) operation.”

Accepted Answer

Introduction / Context: Many PLDs and CPLDs implement logic as sum-of-products fed into macrocell OR arrays. Complex functions may exceed the native product-term budget per output. Vendors therefore provide “expanders” or product-term sharing mechanisms that add more terms to a macrocell’s OR stage without external logic. Given Data / Assumptions: Target architecture: programmable SOP with limited product terms per macrocell. Expanders or product-term allocators are available within the device. Goal: realize wider logic expressions than a single macrocell allows. Concept / Approach: Expanders route additional product terms from neighboring macrocells or from a shared pool into a target macrocell’s OR function. This increases functional capacity while staying on-chip, reducing pin usage and delay compared to external “glue” logic. Step-by-Step Solution: Identify required number of product terms for the intended Boolean function.If it exceeds the per-macrocell limit, enable expanders in the fitter options.The fitter assigns extra terms from adjacent resources into the destination macrocell.Verify timing and resource mapping post-fit. Verification / Alternative check: Compile the design both with and without expanders. Without expanders, the fitter may fail or spill logic externally. With expanders, the fitter reports extra product terms borrowed and a successful fit. Why Other Options Are Wrong: Incorrect: Expanders do increase available product terms. True only for ROM-based PLDs: Product-term expanders are typical of PLA/CPLD-style devices, not restricted to ROM arrays. True only when outputs are registered: Registration is orthogonal to product-term availability. Depends on external glue logic: Expanders reduce the need for external glue. Common Pitfalls: Overusing expanders and creating routing congestion; ignoring timing when pulling terms from distant macrocells; assuming expanders are unlimited. Final Answer: Correct

Question 8

MAX7000S device interconnect architecture: Evaluate the statement — “All inputs to an Altera MAX7000S device and all macrocell outputs feed the Programmable Interconnect Array (PIA).”

Accepted Answer

Introduction / Context: CPLD families such as Altera’s MAX7000S use a central interconnect fabric—the Programmable Interconnect Array (PIA)—to route signals between I/O pins and logic macrocells. Understanding this fabric clarifies how signals are shared, how product terms are allocated, and how global resources integrate across the device. Given Data / Assumptions: Device family: MAX7000S. Macrocells implement sum-of-products with optional registers. PIA is the central routing matrix. Concept / Approach: In this architecture, external inputs (from I/O pins) and macrocell outputs are all made available to the PIA. The PIA then programmably distributes these signals to other macrocells’ product terms and to I/O blocks as needed, enabling flexible interconnect without board-level rewiring. Step-by-Step Solution: Identify PIA as the shared routing resource inside MAX7000S.Confirm that both I/O-pin signals and macrocell outputs enter the PIA.These signals can then be selected as inputs to other macrocells or I/O.Therefore, the statement is correct. Verification / Alternative check: Device block diagrams show I/O pins and macrocell outputs feeding a central interconnect. Fitter reports list PIA resource usage when signals are routed across function blocks. Why Other Options Are Wrong: Incorrect / Only I/O feed PIA / Only macrocells feed PIA: Each omits part of the architecture; both sources feed the PIA. Depends on global clocks: Clock networks are separate from general interconnect and do not affect whether signals feed the PIA. Common Pitfalls: Assuming point-to-point fixed wiring; overlooking PIA capacity and routing delays; not accounting for PIA when analyzing timing closure. Final Answer: Correct

Question 9

Hardware vs. software implementation trade-offs: Evaluate the statement — “A hardware solution is always faster than a software solution for a digital system design.”

Accepted Answer

Introduction / Context: Choosing between hardware and software implementations depends on performance, latency, flexibility, power, cost, and development time. While custom hardware can exploit parallelism and dedicated pipelines, it is not universally faster than software running on optimized processors with caches, SIMD, and accelerators. Given Data / Assumptions: “Hardware” may refer to ASICs, FPGAs, or dedicated coprocessors. “Software” may run on microcontrollers, CPUs, DSPs, or GPUs. Performance depends on algorithm structure and available parallelism. Concept / Approach: Speed is task-dependent. Hardware wins when abundant fine-grained parallelism exists and latency must be minimal. However, modern software platforms can be faster for control-dominated tasks, irregular data structures, or when using high-performance GPUs. Overheads such as I/O, memory bandwidth, and clock constraints also limit hardware throughput. Step-by-Step Solution: Identify algorithm characteristics (compute-bound vs. memory-bound).Assess parallelism and pipeline depth achievable in hardware and software.Compare total-system constraints: memory bandwidth, I/O, latency, and clock rate.Conclude that “always faster” is incorrect; context determines the winner. Verification / Alternative check: Benchmarks show some signal-processing kernels excel on FPGAs, while others run faster on GPUs or CPUs due to clock speeds, caches, and massive parallel cores. Control-oriented tasks often favor software. Why Other Options Are Wrong: Correct: Not correct because speed depends on the task and platform. True only for DSP / above 200 MHz / instruction width only: Each provides an oversimplified rule that ignores memory, I/O, and algorithmic structure. Common Pitfalls: Overlooking data movement costs; ignoring development time and maintainability; assuming clock frequency directly equals performance. Final Answer: Incorrect

Question 10

System integration reality check: Evaluate the statement — “Most complex digital designs combine multiple categories of hardware (e.g., CPUs, FPGAs/CPLDs, ASICs, analog front ends, memory, and interfaces).”

Accepted Answer

Introduction / Context: Modern digital products—from smartphones to industrial controllers—rarely rely on a single hardware category. Designers integrate processing cores, programmable logic, memory hierarchies, power management, and analog subsystems to meet performance, cost, and regulatory goals. Given Data / Assumptions: Target systems are nontrivial and involve multiple functions. Hardware categories include microprocessors, FPGAs/CPLDs, dedicated ASICs, memory, and mixed-signal I/O. Software coexists with hardware to implement features and updates. Concept / Approach: Partitioning assigns time-critical or parallel tasks to programmable logic or accelerators, while control, UI, and high-level algorithms run on CPUs. Memory and interfaces glue subsystems together. This typical heterogeneity underpins cost-effective and scalable designs. Step-by-Step Solution: Identify system requirements (throughput, latency, power, cost).Map functions to appropriate hardware blocks.Integrate via standard buses and protocols (e.g., SPI, I2C, PCIe).Therefore, the statement accurately reflects real-world practice. Verification / Alternative check: Teardowns of consumer devices show SoCs plus PMICs, RF, sensors, memory, and discrete logic. Industrial designs pair MCUs with FPGAs, ADCs/DACs, and isolation interfaces. Why Other Options Are Wrong: Incorrect: Ignores common system partitioning. Only for aerospace / only when software is absent / depends on PCB layers: These constraints are irrelevant or false; heterogeneity is ubiquitous. Common Pitfalls: Overconsolidating into a single device and losing flexibility; underestimating integration complexity and signal integrity; neglecting firmware upgradability. Final Answer: Correct

Question 11

Microcomputer and DSP programmability: Evaluate the statement — “In microcomputer/DSP systems, you can electronically control devices and manipulate data by executing an application-specific program of instructions.”

Accepted Answer

Introduction / Context: Microcomputers (MCUs/CPUs) and digital signal processors (DSPs) are programmable engines that execute instruction streams stored in memory. Through code, they read sensors, process data, and drive actuators or communication interfaces, enabling flexible, updatable system behavior. Given Data / Assumptions: Program instructions reside in nonvolatile or downloadable memory. Peripherals (GPIO, timers, ADC/DAC, UART/SPI/I2C) are available for I/O. DSPs offer specialized instructions for signal math; MCUs offer general-purpose control. Concept / Approach: Software orchestrates hardware blocks: it configures registers, schedules tasks, reacts to interrupts, and manipulates data using arithmetic and logic instructions. This flexibility contrasts with fixed-function hardware, allowing field updates and feature expansion. Step-by-Step Solution: Load or program instruction memory with the application code.Initialize peripherals and configure control registers.Continuously read inputs, compute results, and drive outputs per the algorithm.Thus, software controls devices and manipulates data as stated. Verification / Alternative check: Common examples include motor control firmware on MCUs, audio filtering on DSPs, and protocol stacks managing communication. Code changes alter system behavior without hardware modification. Why Other Options Are Wrong: Incorrect: Ignores fundamental programmability of MCUs/DSPs. Floating-point only / external ROM only / no peripherals: All are unnecessary constraints; fixed-point and internal flash are common, and peripherals are typical but not required to manipulate data in memory. Common Pitfalls: Poor real-time scheduling; inadequate interrupt handling; misconfigured peripherals; assuming software alone can overcome hardware bandwidth limits. Final Answer: Correct

Question 12

Volatility of SRAM technology: Evaluate the statement — “Static RAM (SRAM) technology is volatile.”

Accepted Answer

Introduction / Context: Memory technologies are categorized as volatile (lose data without power) or nonvolatile (retain data). Static RAM (SRAM) is widely used for caches and fast buffers. Knowing its volatility helps designers plan backup strategies and choose appropriate nonvolatile storage for code and persistent data. Given Data / Assumptions: SRAM stores bits using bistable latching elements (typically 6T cells). SRAM requires a stable power supply to preserve cell states. No special nonvolatile mechanism (e.g., floating gate) is present in standard SRAM. Concept / Approach: In SRAM, each bit is maintained by cross-coupled inverters that hold a state as long as power is applied. Removing power collapses the inverters’ states and data is lost. Therefore, SRAM is inherently volatile. Nonvolatile behavior requires technologies like flash, EEPROM, MRAM, FRAM, or battery-backed SRAM modules (the latter remain volatile without the battery). Step-by-Step Solution: Identify storage mechanism: bistable latches needing power.Consider power loss: without Vcc, nodes discharge and states vanish.Conclude: standard SRAM is volatile by design. Verification / Alternative check: Data retention tests show SRAM contents vanish after supply removal, whereas flash retains data. Battery-backed SRAM retains data only while the battery is good, underscoring inherent volatility. Why Other Options Are Wrong: Incorrect: Contradicts fundamental SRAM operation. Only volatile when unclocked: SRAM does not need a clock for retention; it needs power. Nonvolatile if battery-backed: The battery is an external aid; the core cell remains volatile. Becomes nonvolatile above 3.3 V: Voltage level does not change volatility class. Common Pitfalls: Confusing SRAM with DRAM (which needs refresh) or with nonvolatile memories; assuming standby current equals nonvolatility; overlooking data loss during brownouts. Final Answer: Correct

Question 13

Programmable Logic Devices (PLDs) — scope and limits: PLDs simplify digital design, but can a single PLD reasonably satisfy all possible requirements of complex digital circuitry, or are there cases that require larger devices (for example, FPGAs/AS…

Accepted Answer

Introduction / Context: Programmable Logic Devices (PLDs) — including SPLDs (PAL/GAL) and CPLDs — let designers implement custom logic quickly. However, highly complex systems often exceed the capacity, speed, or I/O resources of a single PLD. Understanding when PLDs suffice and when designs demand FPGAs, ASICs, or multiple devices is a key architectural judgment in digital electronics. Given Data / Assumptions: PLDs offer a finite count of macrocells/product terms and limited I/O pins. Large systems may require deep memory blocks, high-speed DSP, or thousands of registers. Performance, power, and cost constraints must be met simultaneously. Concept / Approach: The core idea is resource matching. A device must have enough logic, routing, and I/O to realize the required state machines, datapaths, and interfaces. If a single PLD cannot provide sufficient product terms, flip-flops, or timing margins, engineers select larger devices (CPLD → FPGA) or partition across multiple parts. Some functions (for example, very wide multipliers or embedded RAM) might be unavailable in many PLDs, making an FPGA or ASIC the practical choice. Step-by-Step Solution: Identify functional requirements: state count, combinational width, clock domains.Map to PLD resources: macrocells, product-term budget, global clocks, I/O.Check timing: can the PLD meet setup/hold and f_max at the target voltage and temperature?Evaluate growth: if future features are expected, a larger device or FPGA may be preferable. Verification / Alternative check: Create a quick synthesis targeting the intended PLD family and review resource utilization and timing reports. If utilization nears 100% or timing slack is negative, the single-PLD solution is inadequate. Why Other Options Are Wrong: Incorrect: Claims a single PLD can always meet any requirement, which is unrealistic.Applies only to PALs, not CPLDs: Capacity limits exist at every PLD tier.Applies only to FPGAs, not PLDs: The question concerns PLD limits, not FPGA limits. Common Pitfalls: Overfilling a device and missing timing; underestimating I/O count; ignoring clocking and metastability; overlooking in-system programmability or field updates. Final Answer: Correct

Question 14

GAL devices and reprogrammability: Generic Array Logic (GAL) chips use an EEPROM-based array that is erasable and can be reprogrammed many times (for example, at least 1000 program/erase cycles). Does this characterization hold?

Accepted Answer

Introduction / Context: GAL (Generic Array Logic) devices were introduced as flexible, pin-compatible replacements for one-time programmable PALs. Their key advantage is reprogrammability, enabled by EEPROM technology, which supports many erase/write cycles and simplifies prototyping and field updates. Given Data / Assumptions: GALs store configuration in EEPROM cells. EEPROM supports multiple erase/write cycles (often 1000+). No UV window is required; erasure is electrical. Concept / Approach: Unlike fuse-based PALs (one-time programmable) and UV-erasable EPROMs, GALs allow electrical reprogramming. This means designers can iterate the logic design repeatedly without replacing the chip. The reprogrammability threshold (for example, 1000 cycles) is typical for early-generation EEPROM processes and is sufficient for development and moderate maintenance cycles. Step-by-Step Solution: Confirm memory type: GAL = EEPROM-based configuration.Check endurance: EEPROM endurance commonly ranges from 10^3 to 10^5 cycles depending on process.Implication: device can be re-used across many design iterations.Conclusion: the statement is accurate for standard GAL parts. Verification / Alternative check: Datasheets for GAL16V8/GAL22V10 families list EEPROM-based configuration and typical endurance specs, confirming erasability and reprogram capability well beyond a single cycle. Why Other Options Are Wrong: Incorrect: Conflicts with the fundamental EEPROM-based nature of GALs.Applies only to PROM-based GALs: GALs are not PROM-based; PROMs are one-time programmable.Only true for UV-erasable versions: GALs are electrically erasable; no UV window or lamp is needed. Common Pitfalls: Confusing GALs with classic PALs; assuming UV erasure like EPROMs; ignoring endurance limits when planning frequent in-field updates. Final Answer: Correct

Question 15

Fuse semantics in PLDs (AND/OR arrays): Consider how “blown” versus “intact” fuses affect connectivity in programmable AND/OR planes. Is it correct to claim: “A blown fuse at an OR gate is a LOW, and a blown fuse at an AND gate is a HIGH” as a unive…

Accepted Answer

Introduction / Context: Programmable Logic Devices implement sum-of-products logic using programmable interconnects in AND/OR arrays (for example, PLA, PAL, PROM). Fuses (or antifuses/EEPROM links) determine whether a literal connects to a product term or whether a product term connects to an OR output. Understanding what a “blown” fuse means is about connectivity, not an absolute HIGH or LOW logic level at a gate. Given Data / Assumptions: Fuse state controls presence/absence of a connection. AND plane connections include literals or their complements; absence yields don’t-care for that literal. OR plane connections sum selected product terms; absence means that term does not contribute. Concept / Approach: In classical fuse-based PLDs, an intact fuse implies a connection; a blown fuse removes it. This does not directly translate to a literal HIGH or LOW level. In the AND array, including a literal constrains the product term; removing it produces a don’t-care (neither forced HIGH nor forced LOW). In the OR array, removing a product-term connection simply means that term does not feed the OR sum. Therefore, the statement that a blown fuse “is LOW” in one plane and “is HIGH” in the other is an oversimplification and is not a universal rule. Step-by-Step Solution: Treat fuse state as connectivity control, not a logic level source.In AND plane: intact = include literal; blown = omit literal → don’t-care.In OR plane: intact = include product term; blown = omit term → it contributes nothing.Hence, no universal “blown = LOW/HIGH” mapping exists. Verification / Alternative check: Reference any PLA/PAL fuse map description: the programming matrix shows presence/absence of connections, not fixed logic levels at the logic gates. Why Other Options Are Wrong: Correct: Mischaracterizes connectivity as a fixed logic level.Correct only for PROM-based OR planes / PAL-based AND planes: Still confuses connection absence with a forced logic level. Common Pitfalls: Assuming removing a literal forces a term HIGH; ignoring that “don’t-care” broadens the minterm rather than driving a constant level. Final Answer: Incorrect

Question 16

Schematic editors in PLD/FPGA toolflows: Does a schematic editor allow designers to connect circuits using predefined logic symbols (for example, AND/OR/XOR, registers, I/O buffers) rather than writing code?

Accepted Answer

Introduction / Context: Digital design toolchains commonly offer multiple entry methods: schematic capture, hardware description languages (VHDL/Verilog), and block-based design. Schematic editors remain useful for small designs, education, or when visual clarity is preferable to code-centric entry. Given Data / Assumptions: A library of predefined logic symbols is provided by the tool. Designers can place, wire, and hierarchically organize symbols. Netlists generated from schematics feed into synthesis and fitting. Concept / Approach: Schematic editors provide a graphical environment to instantiate gates, flip-flops, arithmetic blocks, and IP cores. Designers connect symbols with nets, assign constraints, and simulate the resulting netlist. The flow parallels HDL-based design, with the editor replacing textual description for connectivity. Step-by-Step Solution: Open schematic editor and select symbols from the library.Place gates/registers and route connections as required.Add I/O symbols and constraints; generate a netlist.Run synthesis/fitting and verify through simulation or on hardware. Verification / Alternative check: Most FPGA/PLD IDEs include schematic capture examples and allow mixed flows, where schematics instantiate HDL blocks and vice versa. Why Other Options Are Wrong: Incorrect: Schematic capture is a standard digital entry method.Only for analog / ASIC back-end: Digital schematic capture is common across many vendor toolchains. Common Pitfalls: Large systems become unwieldy on schematics; version control and text diffs are harder than HDL-based flows; portability across tools can be limited. Final Answer: Correct

Question 17

Gate arrays and ULSI scale: Are gate arrays considered ultra-large-scale integration (ULSI) devices that can offer on the order of hundreds of thousands of gates (or more, depending on process)?

Accepted Answer

Introduction / Context: Gate arrays (including sea-of-gates and structured ASIC variants) pre-allocate arrays of transistors or gates, later customized by metal interconnect layers. Historically and in modern forms, they target large digital functions far beyond simple SSI/MSI capacities, falling into the LSI/VLSI/ULSI spectrum depending on era and process node. Given Data / Assumptions: ULSI describes very high gate counts on a single die. Gate arrays are fabricated with regular fabrics and customized interconnect. Process scaling increases feasible gate counts dramatically. Concept / Approach: By leveraging pre-fabricated arrays, designers can integrate extensive logic while reducing turnaround relative to full-custom ASICs. Even older processes reached hundreds of thousands of gates; modern structured ASICs exceed that by orders of magnitude. Thus, describing gate arrays as ULSI for many applications is accurate. Step-by-Step Solution: Classify integration scale: SSI < MSI < LSI < VLSI < ULSI.Map gate arrays: typically VLSI to ULSI, depending on generation.Confirm capacity: hundreds of thousands to millions of equivalent gates are common historically and higher today.Conclusion: the statement is correct. Verification / Alternative check: Consult classic gate-array datasheets and structured ASIC literature showing large logic capacities and high I/O counts. Why Other Options Are Wrong: Incorrect: Understates the realistic capacity of gate arrays.SSI-only / analog-only: Misclassifies the technology and its use cases. Common Pitfalls: Equating gate arrays with small PLDs; ignoring that “gate count” metrics vary with reference cell definitions. Final Answer: Correct

Question 18

Product-term borrowing in MAX+PLUS II (Altera CPLDs): Does the compiler automatically allow a macrocell to borrow up to six product terms from each of three adjacent macrocells in the same Logic Array Block (LAB)?

Accepted Answer

Introduction / Context: Altera (now Intel) MAX-series CPLDs use product-term macrocells grouped into Logic Array Blocks (LABs). The tools support product-term sharing/expansion to realize wider logic equations than a single macrocell can natively implement. However, the exact borrowing limits depend on family architecture and are not universally “six from each of three adjacent macrocells.” Given Data / Assumptions: MAX+PLUS II supports product-term expansion within a LAB. Borrowing limits vary by family (for example, MAX 7000/9000). The quoted “six from each of three adjacent macrocells” is a very specific claim. Concept / Approach: While product-term sharing is real, vendor documentation specifies totals and patterns that differ across devices. Some families allow a macrocell to gain a defined number of additional product terms via expanders, but the numbers and topology constraints (which neighbor, how many, how routed) are architecture-specific. The statement’s exact figures do not represent a general rule for MAX+PLUS II across all CPLDs and are therefore unreliable as a blanket assertion. Step-by-Step Solution: Recognize that expansion exists but is architecture-bound.Compare to datasheets: totals and adjacency rules vary by device.Note that the claim offers specific counts not consistently documented across families.Conclude the universal claim is incorrect. Verification / Alternative check: Check the specific MAX family datasheet and the Compiler Help. You will find product-term expansion descriptions, but not a universal “6 from each of 3 neighbors” rule. Why Other Options Are Wrong: Correct: Overstates a family-independent behavior with exact counts.Family- or JTAG-conditional claims: JTAG does not govern product-term borrowing limits; limits are architectural. Common Pitfalls: Memorizing a number from one family and generalizing to all; ignoring fitter reports that show actual product-term usage. Final Answer: Incorrect

Question 19

Basic VHDL source structure: Is it accurate to summarize typical VHDL code as having three main sections in order: library/use clauses, an entity declaration, and an architecture body?

Accepted Answer

Introduction / Context: VHDL describes hardware with a well-defined, modular structure. While files can contain multiple design units, a common pattern is to include library/use clauses, followed by an entity (interface) and an architecture (implementation). Recognizing this structure helps newcomers read and write synthesizable designs. Given Data / Assumptions: Library/use clauses import packages and types (for example, IEEE.STD_LOGIC_1164). Entity declares ports and generics (the interface). Architecture defines behavior/structure corresponding to that entity. Concept / Approach: The entity/architecture split mirrors interface/implementation concepts in software but maps directly to hardware. The architecture can be behavioral, dataflow, or structural and may contain processes, concurrent statements, and component instantiations. Additional design units (configurations, packages) may appear, but the “library + entity + architecture” trio is the standard minimum for a synthesizable design unit. Step-by-Step Solution: Write library/use statements to import needed packages.Declare entity with generics and ports.Implement architecture referencing the entity’s interface.Optionally add configurations or package bodies as separate units. Verification / Alternative check: Open any basic VHDL example from vendor templates; you will observe this structure. Simulators and synthesizers expect design units in this canonical form. Why Other Options Are Wrong: Incorrect: Neglects the standard entity/architecture pairing.Testbench-only / generics-only: The structure applies broadly, not just to special cases. Common Pitfalls: Forgetting library/use clauses; mismatching entity/architecture names; mixing multiple entities/architectures in one file without managing design unit visibility. Final Answer: Correct

Question 20

JTAG interface signal names: Does the Joint Test Action Group (JTAG/IEEE 1149.1) boundary-scan interface use the signals TDI, TDO, TMS, and TCK as its primary pins?

Accepted Answer

Introduction / Context: JTAG (IEEE 1149.1) defines a standard boundary-scan architecture and a serial test access port (TAP). The TAP enables testing, programming, and debugging through a small set of well-known signals used on PLDs, FPGAs, microcontrollers, and ASICs. Given Data / Assumptions: TDI: Test Data In. TDO: Test Data Out. TMS: Test Mode Select (controls TAP state machine). TCK: Test Clock (clocks the TAP). Concept / Approach: The TAP controller is a defined state machine advanced by TCK and TMS. TDI and TDO form the serial data path through the instruction and data registers. Many devices also implement optional TRST (Test Reset). These signal names are standardized in the specification and appear consistently in datasheets and programming cables. Step-by-Step Solution: Identify TAP pins by function and standardized names.Relate them to operations: shifting instructions/data, capturing, updating.Confirm optional signals (for example, TRST) are not always present.Conclude that TDI, TDO, TMS, and TCK are the primary signals. Verification / Alternative check: Vendor boundary-scan descriptions and programming cables label these signals consistently. IEEE 1149.1 documentation uses these exact names. Why Other Options Are Wrong: Incorrect / only TDI/TDO: Ignores the control and clock pins needed for TAP state control.CLK/DIN/DOUT/MODE: Non-standard names not used by the IEEE standard. Common Pitfalls: Confusing TAP with SPI; miswiring TMS/TCK and preventing chain detection; ignoring pull-ups recommended on TMS/TDI. Final Answer: Correct

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