Question 1

Terminology in Boolean implementation “The Boolean sum of four product terms is called a sum-of-products (SOP) expression.” Evaluate the correctness of this definition in digital logic design.

Accepted Answer

Introduction / Context: Sum-of-products (SOP) and product-of-sums (POS) are foundational canonical forms in Boolean algebra, widely used in minimization and hardware realization (e.g., PAL/CPLD macrocells). This item checks fundamental terminology. Given Data / Assumptions: We have several product terms (ANDed literals) combined by OR operations. Example mentions four product terms, but the count is not critical to the definition. We assess whether such an OR of product terms is an SOP. Concept / Approach: An SOP expression is defined as the Boolean OR (sum) of one or more Boolean product terms. A product term is an AND of literals (variables or their complements). Whether the products are minterms (all variables present) or implicants (subset of variables) does not change the “SOP” classification. Therefore, the “sum of four product terms” is indeed an SOP expression. Step-by-Step Solution: Identify structure: term1 + term2 + term3 + term4, where each term is an AND of literals.Match to definition: sum (OR) of products (ANDs) ⇒ SOP.Conclude the statement is correct. Verification / Alternative check: Textbook minimization via Karnaugh maps or Quine–McCluskey ultimately produces SOP or POS; both accept arbitrary numbers of terms. Why Other Options Are Wrong: “Incorrect” contradicts definitions. “Only for Karnaugh maps” is untrue; SOP is a Boolean form independent of method. Requiring minterms is unnecessary; any product terms qualify. Common Pitfalls: Confusing minterms with general products; believing SOP implies a unique minimal form—it does not; minimization reduces but does not redefine the SOP structure. Final Answer: Correct

Question 2

PAL implementation capability “The PAL (Programmable Array Logic) structure is able to perform any sum-of-products (SOP) operation.” Decide whether this absolute claim is accurate.

Accepted Answer

Introduction / Context: PAL and PLA devices both realize SOP logic, but with different arrays. A PAL has a programmable AND array and a fixed OR array (with limited product terms per output), whereas a PLA has both arrays programmable. This difference affects which SOP expressions can be implemented directly. Given Data / Assumptions: Device: PAL (programmable AND, fixed OR). Claim: can perform any SOP expression. We consider limits such as available product terms and fixed interconnect. Concept / Approach: “Any SOP” would imply no structural limitations. In a PAL, each output has a fixed number of OR inputs, so only a limited number of product terms can feed that output directly. If an SOP requires more product terms than allowed, the expression cannot be implemented in a single PAL output without logic factoring or cascading devices. A PLA, with a programmable OR array, is closer to realizing arbitrary SOP (still bounded by available terms), but PALs are more restricted by design. Step-by-Step Solution: Recall PAL architecture: programmable AND, fixed OR with limited inputs.Compare with the requirement “any SOP.”Conclude the absolute claim is false due to product-term limits. Verification / Alternative check: Device datasheets for PALs list maximum product terms per output; exceeding that limit requires redesign (e.g., factoring, sharing, or a larger device). Why Other Options Are Wrong: “Correct” ignores hard limits. “Only correct for PLA” better reflects programmability differences but still depends on term counts. “True with unlimited terms” acknowledges the caveat but typical PALs do not offer unlimited terms. Common Pitfalls: Assuming “can perform SOP” implies “can perform any SOP”; conflating ideal logic forms with practical device constraints. Final Answer: Incorrect

Question 3

In programmable logic terminology, SPLD stands for Simple Programmable Logic Device, not a coding language. Evaluate the statement: “SPLD is a program language used by PLD software.” Decide whether this description is accurate in the context of digi…

Accepted Answer

Introduction / Context: Programmable logic devices (PLDs) are categorized into families and device classes such as SPLD, CPLD, and FPGA. The statement under review claims that SPLD is a “program language used by PLD software.” This question tests your ability to distinguish between device-class acronyms and hardware description languages used to configure them. Given Data / Assumptions: SPLD is an established term in digital electronics. PLD software uses languages or entry methods (e.g., schematic, CUPL, ABEL, VHDL, Verilog) to describe logic. The goal is to decide whether SPLD refers to a language or to a device category. Concept / Approach: SPLD expands to “Simple Programmable Logic Device,” a class of small programmable devices (e.g., PAL, GAL). By contrast, programming or design entry uses languages like ABEL/CUPL (historical), or HDL languages such as VHDL/Verilog. Therefore, the statement confuses a device class with a language. Step-by-Step Solution: Identify the acronym SPLD → Simple Programmable Logic Device (hardware class).Recall languages used by PLD software → not SPLD; examples include VHDL/Verilog/ABEL/CUPL.Conclude the statement equates a device class to a language → inaccurate. Verification / Alternative check: Check vendor literature: SPLD appears in device datasheets; languages appear in tool documentation. Why Other Options Are Wrong: Correct: Would wrongly accept the misdefinition.Partially correct under vendor-specific conditions: No vendor uses SPLD as a language.Obsolete statement; replaced by newer standard: It was never a language, so not merely obsolete. Common Pitfalls: Confusing device families (SPLD/CPLD/FPGA) with design-entry languages.Assuming any PLD-related acronym must be a language. Final Answer: Incorrect

Question 4

PAL structure versus PROM: In a PAL, the AND array is programmable while the OR array is fixed (hard-wired). Assess the accuracy of the statement comparing PAL and PROM internal AND/OR structures.

Accepted Answer

Introduction / Context: Programmable logic families differ primarily in which internal arrays (AND or OR) are field-programmable. Understanding these differences is key when choosing devices for sum-of-products logic implementations and product-term budgeting. Given Data / Assumptions: PROMs have a fixed AND (decoder) array and a programmable OR array. PALs (Programmable Array Logic) feature a programmable AND array and a fixed (hard-wired) OR array. FPLAs/PLAs typically have both AND and OR arrays programmable. Concept / Approach: The question asserts the classic textbook distinction: PAL → programmable AND, fixed OR. PROM → fixed AND (as a decoder), programmable OR fuses. Recognizing this mapping lets designers predict resource use and optimal device choice. Step-by-Step Solution: Recall PROM structure: fixed AND (decoder), programmable OR fuses.Recall PAL structure: programmable AND product terms, hard-wired OR structure.Compare with the statement → matches PAL definition → accurate. Verification / Alternative check: Cross-check with vendor datasheets or digital design textbooks; the PAL definition is consistent across sources. Why Other Options Are Wrong: Incorrect: Contradicts widely accepted PAL architecture.Partially correct; depends on speed grade: Speed grade does not change array programmability.Ambiguous; neither array is programmable: Opposite of reality for PALs. Common Pitfalls: Confusing PAL with PLA/FPLA, where both arrays may be programmable.Assuming “programmable” refers to RAM-based LUTs (that is FPGA terminology). Final Answer: Correct

Question 5

Altera MAX7000S CPLD family I/O architecture: Every I/O pin includes a configurable tri-state output buffer. Judge the correctness of this statement about MAX7000S device pins and their output-enable control.

Accepted Answer

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: MAX7000S devices provide configurable I/O pins. Tri-state output buffers are standard in IOEs for bus sharing. Special-purpose pins (e.g., configuration, power) are not counted as general I/O. 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

Question 6

Acronym check in digital logic: “LUT” correctly expands to “look-up table.” Indicate whether this terminology usage is accurate in FPGA/CPLD contexts.

Accepted Answer

Introduction / Context: LUTs are the basic logic resources in many FPGA architectures and also appear conceptually in CPLDs and synthesis discussions. This question checks recognition of a core acronym encountered in vendor literature and academic texts. Given Data / Assumptions: LUT is a small memory that maps input address bits to a stored output bit pattern. Vendors use “LUT” consistently to mean “look-up table.” The term is not limited to any one vendor or family. Concept / Approach: A look-up table implements combinational functions by storing truth-table entries. For n inputs, the LUT stores 2^n output values. Synthesis tools map boolean logic to LUTs in FPGAs, making this acronym central to modern digital design. Step-by-Step Solution: Recall LUT definition → memory-based truth-table element.Map to term expansion → LUT = look-up table.Conclude the statement correctly reflects industry usage. Verification / Alternative check: Check any FPGA architecture overview; LUT terminology is universal. Why Other Options Are Wrong: Incorrect: Would deny a standard expansion.Legacy definition; modern usage differs: The meaning has remained consistent.Applies only to ASIC standard cells: LUTs are FPGA-centric, not ASIC standard-cell primitives. Common Pitfalls: Confusing LUT with RAM blocks or ROM macros; LUTs are tiny and used for arbitrary logic mapping. Final Answer: Correct

Question 7

Sum-of-Products (SOP) form definition: SOP means product terms combined by OR (sum), not NAND. Evaluate the statement: “Sum-of-products is two or more product terms that are NANDed together.”

Accepted Answer

Introduction / Context: Canonical boolean forms are foundational to logic design, logic minimization, and PLD device mapping. Understanding the exact meaning of Sum-of-Products (SOP) versus Product-of-Sums (POS) is essential, especially when targeting PAL/PLA resources or writing HDL that maps cleanly to product terms. Given Data / Assumptions: SOP consists of product terms (ANDed literals) summed via OR. Physical NAND-NAND realizations can implement an SOP function due to De Morgan’s transformations, but the formal SOP definition remains OR of products. Terminology refers to algebraic structure, not the gate-level optimization chosen. Concept / Approach: The algebraic definition of SOP is: F = P1 + P2 + ... + Pn, where each Pi is a product term like (a*b*c). While hardware might use NAND gates to implement this efficiently, that does not change the mathematical definition that the top-level operation is OR (sum). Step-by-Step Solution: Define product term → AND of literals (e.g., a*b).Define SOP → OR of product terms (e.g., a*b + a*c + b*c).Compare with the statement (NANDed together) → does not match SOP definition → incorrect. Verification / Alternative check: Convert a NAND-NAND network to its algebraic form; you recover an OR of products after inversion cancellation. Why Other Options Are Wrong: Correct: Contradicts the canonical definition.Only correct in NAND-NAND implementations: Hardware choice does not redefine SOP algebra.Context-dependent: While gates vary, algebraic naming does not. Common Pitfalls: Equating gate-level choices (NAND) with algebraic labels (SOP).Forgetting that “sum” means OR in boolean algebra. Final Answer: Incorrect

Question 8

MAX7000S device blocks: The family uses Logic Array Blocks (LABs) and a Programmable Interconnect Array (PIA), not “intermediate.” Decide whether the term “programmable intermediate array” is correct for MAX7000S.

Accepted Answer

Introduction / Context: Vendor-specific block names matter when reading handbooks and constraint guides. The MAX7000S CPLD family features macrocells organized in LABs connected by a routing fabric formally called the Programmable Interconnect Array (PIA). Given Data / Assumptions: MAX7000S uses LABs for logic macrocells. The routing matrix is termed “Programmable Interconnect Array.” The phrasing “programmable intermediate array” is not the standard name. Concept / Approach: Precision in nomenclature avoids confusion with other families or academic abstractions. The correct expansion of PIA is interconnect, not intermediate. Misnaming can cause misinterpretation when consulting pin-locking or timing models tied to the actual interconnect. Step-by-Step Solution: Identify MAX7000S major blocks: LAB + PIA.Expand PIA correctly: Programmable Interconnect Array.Compare with the statement (“intermediate”) → mismatch → incorrect. Verification / Alternative check: Check a MAX7000S datasheet overview; the routing network is consistently “interconnect.” Why Other Options Are Wrong: Correct: Would endorse the wrong term.Partially correct: Terminology is not vendor-variable here; it is specific.Applies only to MAX3000: Not relevant; still “interconnect.” Common Pitfalls: Mixing generic phrases with vendor-official block names.Assuming “PIA” can flexibly expand to similar-sounding words. Final Answer: Incorrect

Question 9

GAL16V8 OLMC feedback path: In the Output Logic Macrocell, the FMUX selects which signal is fed back into the device’s input matrix. Assess whether this description is accurate for the GAL16V8 architecture.

Accepted Answer

Introduction / Context: Generic Array Logic (GAL) devices such as the GAL16V8 organize logic around Output Logic Macrocells (OLMCs). A key feature is a feedback multiplexer (often labeled FMUX) that determines what signal is returned to the AND array (input matrix) for building more complex equations. Given Data / Assumptions: GAL16V8 OLMCs support combinatorial and registered modes. Feedback can source from the macrocell output, internal node, or registered output depending on mode. The FMUX selects the feedback source that re-enters the input matrix (AND array). Concept / Approach: The feedback path enables product terms in one macrocell to reference the result of another, supporting multi-level logic within the constraints of a PLA-like structure. The FMUX is the selector that chooses which internal signal is fed back. Step-by-Step Solution: Identify OLMC components: product-term OR, optional register, output buffer, feedback mux.Confirm FMUX role: chooses feedback source (registered or combinatorial).Therefore, the statement matches the architecture → accurate. Verification / Alternative check: Consult a GAL16V8 functional block diagram; a selectable feedback path to the AND array is clearly shown. Why Other Options Are Wrong: Incorrect: Contradicts documented macrocell behavior.Only true for registered mode: Feedback exists for both modes (source differs).Applies only to active-LOW paths: Polarity control is separate from feedback selection. Common Pitfalls: Assuming feedback always equals the pin state; internal selection may differ.Confusing input matrix (AND plane) with external pin routing. Final Answer: Correct

Question 10

PAL device pins: Tri-state buffers are associated with outputs/bidirectional pins, not with dedicated input pins. Evaluate the statement: “Most PAL devices have a tristate buffer driving the input pins.”

Accepted Answer

Introduction / Context: Tri-state output buffers provide three states—drive HIGH, drive LOW, or high-impedance (Hi-Z)—and are essential for bus sharing. Inputs, however, are receivers; they do not drive buses and therefore do not require tri-state output drivers. Given Data / Assumptions: PAL devices offer output macrocells with optional tri-state control via an output-enable equation. Dedicated input pins terminate in input buffers and protection networks, not output drivers. Some pins may be configurable as I/O; tri-state applies when the pin is used as an output. Concept / Approach: The phrase “driving the input pins” is contradictory: input pins do not drive; they are driven by external sources. Tri-state drivers belong to output paths (and bidirectional pins when configured as outputs). Hence, saying that PALs have tri-state buffers on input pins is incorrect. Step-by-Step Solution: Define tri-state → attribute of output drivers to enter Hi-Z.Identify input pins → receive signals via input buffers; no output driver present.Conclude statement is false: tri-state buffers do not “drive” inputs. Verification / Alternative check: Examine PAL pin function tables: outputs have OE equations; inputs do not. Why Other Options Are Wrong: Correct: Would wrongly assign output hardware to inputs.Only true for Schmitt-trigger inputs: Schmitt inputs shape edges; they do not add output drivers.True for power pins only: Power pins are neither inputs nor outputs. Common Pitfalls: Confusing “bidirectional pins” configured as outputs with dedicated inputs.Assuming every pad cell contains a tri-state driver regardless of direction. Final Answer: Incorrect

Question 11

FPLA/PLA architecture: A Field-Programmable Logic Array has both a programmable AND array and a programmable OR array. Determine whether this statement is accurate for classic FPLA devices.

Accepted Answer

Introduction / Context: Understanding the distinctions among PROM, PAL, and PLA/FPLA devices helps in selecting the right programmable logic for a given logic function. The key question is which internal planes (AND/OR) are programmable. Given Data / Assumptions: PROM: fixed AND (decoder), programmable OR. PAL: programmable AND, fixed OR. PLA/FPLA: programmable AND and programmable OR. Concept / Approach: A PLA (and its field-programmable variant, FPLA) offers flexibility by allowing both product term creation (AND plane) and their combination (OR plane) to be programmed. This supports complex logic sharing and minimizes redundant product terms relative to PALs. Step-by-Step Solution: Identify device: FPLA → both arrays programmable.Compare with statement → matches → accurate.Infer design implications: more flexibility, potentially larger area/delay than PAL. Verification / Alternative check: Textbook block diagrams show programmable fuses/links in both planes for PLAs/FPLAs. Why Other Options Are Wrong: Incorrect: Opposes standard definition.Only AND programmable: Describes PALs, not PLAs.Only OR programmable: Describes PROMs, not PLAs. Common Pitfalls: Conflating PAL and PLA capabilities when minimizing logic.Ignoring that flexibility often increases resource usage and timing. Final Answer: Correct

Question 12

GAL22V10 device pinout: The part provides 10 macrocells (outputs) and up to 12 dedicated inputs — not 12 outputs and 10 inputs. Judge the correctness of the statement about GAL22V10 pin counts.

Accepted Answer

Introduction / Context: Part-number mnemonics in classic GAL devices often hint at available resources. For the GAL22V10, “22” indicates the maximum number of usable input signals into the logic array, and “10” indicates the number of macrocells (potential outputs). Given Data / Assumptions: GAL22V10 contains 10 OLMC macrocells capable of driving outputs. Up to 12 pins function as dedicated inputs into the AND array. Package pin count and special pins (e.g., clock, OE) are not misinterpreted as outputs. Concept / Approach: The statement claims 12 outputs and 10 inputs, which is reversed from standard device documentation. Correctly, the device provides 10 outputs (macrocells) and 12 inputs to reach the nominal “22” total signals into the array. Step-by-Step Solution: Parse device code: 22V10 → 22 input terms, 10 outputs/macrocells.Map to pins: 10 outputs possible; 12 dedicated inputs available.Compare with statement → reversed → therefore incorrect. Verification / Alternative check: Check a GAL22V10 datasheet: pin tables and functional diagrams confirm 10 OLMC outputs. Why Other Options Are Wrong: Correct: Would accept the reversed counts.Depends on security-bit programming: Security bits do not change macrocell counts.Only true for QFP variant: Packaging does not invert core resources. Common Pitfalls: Confusing “22” as output count rather than input term count into the array.Misreading bidirectional pin capability as dedicated outputs in all modes. Final Answer: Incorrect

Question 13

CPLD programming technologies: Evaluate the statement — “The programming technologies used in Complex Programmable Logic Devices (CPLDs) are all nonvolatile (retain configuration without power).”

Accepted Answer

Introduction / Context: CPLDs (Complex Programmable Logic Devices) are widely used where instant-on behavior and deterministic timing are desired. This item checks whether you know that mainstream CPLD configuration technologies are nonvolatile, meaning the device powers up already configured without loading a bitstream from external memory. Given Data / Assumptions: CPLDs commonly use EEPROM or Flash to store configuration. “Nonvolatile” means configuration persists without power. We are discussing configuration storage technology, not user RAM. Concept / Approach: CPLDs historically evolved from SPLDs with electrically erasable programming. Unlike most SRAM-based FPGAs, which need a configuration load on every boot, CPLDs retain their logic equations internally. This enables true instant-on and simplifies board design by removing the need for external configuration PROMs in many cases. Step-by-Step Solution: Identify common CPLD families (e.g., Flash/EEPROM-based).Note that their configuration cells keep data without power.Conclude that the statement is accurate: CPLD programming tech is nonvolatile. Verification / Alternative check: Compare CPLDs with SRAM FPGAs that require bitstreams from external Flash. CPLDs do not need this step because their internal nonvolatile cells already store the design. Why Other Options Are Wrong: Incorrect: Conflicts with standard CPLD technology (EEPROM/Flash). True only for EEPROM-based CPLDs: Flash-based CPLDs are also nonvolatile. Battery attachment: Nonvolatility here is intrinsic, not battery-backed. JTAG speed: JTAG is for programming, unrelated to retention with power off. Common Pitfalls: Confusing CPLDs with SRAM FPGAs; assuming “needs configuration” equals “volatile”; overlooking instant-on benefits for control logic and glue logic. Final Answer: Correct

Question 14

PAL architecture clarification: Evaluate the statement — “A PAL uses a programmable OR array followed by a fixed AND array.”

Accepted Answer

Introduction / Context: Programmable Array Logic (PAL) devices are classic SPLDs whose internal structure every digital designer should know. This question tests whether you can correctly identify which array is programmable and which is fixed inside a PAL device. Given Data / Assumptions: PAL devices implement sum-of-products logic. Two core arrays exist: AND array and OR array. Only one of these arrays is programmable in a standard PAL. Concept / Approach: In a PAL, the AND array is programmable (you can form the needed product terms), while the OR array is fixed (each output has a fixed number of product-term inputs it can sum). This is the reverse of a PLA, which has both arrays programmable. Therefore, the statement claiming a programmable OR and fixed AND is wrong. Step-by-Step Solution: Recall PAL internal structure: programmable AND, fixed OR.Compare with statement (programmable OR, fixed AND).Mismatch implies the statement is incorrect. Verification / Alternative check: Consult typical PAL16L8/PAL16R8 block diagrams: fusible links appear at the AND plane, not the OR plane. OR resources are predetermined per output macrocell. Why Other Options Are Wrong: Correct: Not correct because it reverses PAL internals. True only for GAL: GALs mimic PAL behavior while adding reprogrammability, not swapping array roles. Tri-stated outputs / fuse polarity: Output options and fuse polarity do not change which array is programmable. Common Pitfalls: Confusing PAL with PLA; assuming both arrays are programmable in every SPLD; ignoring fixed product-term limits per output. Final Answer: Incorrect

Question 15

FPGA hard-core reprogrammability claim: Evaluate the statement — “The hard-core portions of FPGAs are reprogrammable in the field.”

Accepted Answer

Introduction / Context: Modern FPGAs include two types of resources: configurable fabric (LUTs, routing) and fixed-function “hard cores” (e.g., SERDES, PLLs, multipliers, sometimes embedded CPUs). This question ensures you can distinguish configuration of the fabric from the non-reprogrammable nature of hard silicon blocks. Given Data / Assumptions: Hard cores are fixed at manufacture (mask-defined). Configurable logic is programmed via bitstreams. Field updates affect configuration, not transistor-level hard-macro design. Concept / Approach: “Reprogrammable” means you can change logic function after deployment. While the configurable fabric is indeed reprogrammable, hard cores are part of the chip’s permanent silicon. You can configure how those hard cores operate (e.g., set PLL multipliers), but you cannot reprogram their fundamental logic implementation in the field. Step-by-Step Solution: Identify hard cores (e.g., transceivers) as fixed hardware blocks.Recognize that bitstreams drive LUTs and routing, not redesign hard silicon.Conclude the statement is incorrect: hard cores are not reprogrammable; only configurable. Verification / Alternative check: Device datasheets separate “hard IP” (fixed) from “soft IP” (implemented in LUTs). Only soft IP changes with a new bitstream. Hard IP parameters are adjustable but the logic gates remain unchanged. Why Other Options Are Wrong: Correct / only for DSP / partial reconfiguration: All confuse parameterization with reprogramming of hard silicon. JTAG fuses: Affect access and security, not the hard macro’s reprogrammability. Common Pitfalls: Equating “configurable” with “reprogrammable hard core”; assuming partial reconfiguration can alter hard IP composition; overlooking the difference between soft IP and hard IP. Final Answer: Incorrect

Question 16

Digital design categories overview: Evaluate the statement — “Major digital system categories include Boolean logic, ASICs, and microprocessor/DSP devices.”

Accepted Answer

Introduction / Context: Digital systems can be organized by implementation style and flexibility: fixed Boolean logic (standard logic ICs/PLDs), custom silicon (ASICs), and programmable computing engines (microprocessors and DSPs). The statement captures a common high-level grouping used in curriculum and practice. Given Data / Assumptions: “Boolean logic” covers discrete logic, SPLDs, and small CPLDs. “ASICs” represent application-specific integrated circuits, including standard-cell and structured arrays. “Microprocessor/DSP” covers programmable instruction-executing devices. Concept / Approach: At system partitioning time, engineers decide what to realize with fixed logic (deterministic, low latency), with custom silicon (performance/power/volume), or with programmable processors (flexibility, fast development). This taxonomy is practical and widely used. Step-by-Step Solution: Recognize Boolean logic, ASICs, and microprocessor/DSPs as canonical categories.Note that FPGAs/PLDs bridge Boolean logic and ASIC-like behavior.Therefore, the statement is acceptable and correct. Verification / Alternative check: Industry product teardowns and textbooks reflect these categories: standard logic glue, domain-specific ASICs, and general-purpose programmable processors or DSPs. Why Other Options Are Wrong: Incorrect / academic only / embedded only: These dismiss realistic, widely applied categorization. Depends on PLDs: PLDs fit under Boolean logic or as a distinct programmable logic subcategory without negating the statement. Common Pitfalls: Believing categories are mutually exclusive; forgetting hybrids (SoCs with CPU + FPGA fabric); overlooking that the best solution often mixes categories. Final Answer: Correct

Question 17

Classify the Boolean form: For the expression (A + B)(C + D), identify the canonical style of logic representation.

Accepted Answer

Introduction / Context: Recognizing whether a Boolean expression is in Sum-of-Products (SOP) or Product-of-Sums (POS) form is foundational for logic minimization, mapping to PLDs/CPLDs, and interpreting Karnaugh maps. This recognition influences how you group terms and implement gates. Given Data / Assumptions: Expression is (A + B)(C + D). “+” denotes logical OR; adjacency denotes logical AND. We classify the overall structural form. Concept / Approach: SOP means “OR of AND terms” (e.g., AB + A’C). POS means “AND of OR terms” (e.g., (A + B)(C + D)). Since our expression is an AND between two sums, it is POS. Correct identification helps when mapping expressions to gate-level or array-level structures. Step-by-Step Solution: Observe the outermost operation: terms are multiplied (ANDed).Each multiplicand is a sum (OR) of literals.AND of sums is by definition Product-of-Sums (POS). Verification / Alternative check: Expanding (A + B)(C + D) yields AC + AD + BC + BD, which is SOP after expansion; however, the original, unexpanded structural form is POS. Structural form is judged before algebraic expansion. Why Other Options Are Wrong: SOP: Not in original structural form. LUT / LAB / PLA form: These are implementation terms or device blocks, not canonical expression styles. Common Pitfalls: Confusing expanded form with original form; assuming only one correct representation exists; overlooking that K-map grouping often moves between SOP and POS depending on 1-cells vs. 0-cells. Final Answer: POS

Question 18

Identify the device type: A complex programmable logic device built from multiple SPLD/PLD blocks with programmable interconnections is called a ________.

Accepted Answer

Introduction / Context: Programmable logic spans from simple SPLDs to large CPLDs and FPGAs. Knowing the architectural composition helps you choose the right device for density, speed, and ease of routing. Given Data / Assumptions: Device consists of several SPLD-like arrays (e.g., AND/OR macrocells). There is a programmable interconnect fabric linking these blocks. We are not describing a full FPGA fabric of LUTs and rich routing. Concept / Approach: A CPLD integrates multiple SPLD-style macrocells into function blocks, then links them via a programmable interconnect matrix. This provides more capacity and better global timing than a single SPLD while preserving nonvolatile, instant-on behavior in many families. Step-by-Step Solution: Match architectural traits (SPLD blocks + interconnect) to known device classes.Eliminate test/fixture terms like boundary scan or bed-of-nails.Select CPLD as the correct term. Verification / Alternative check: Vendor block diagrams (e.g., MAX7000, XC9500) show logic array blocks connected through a central matrix—exactly the CPLD hallmark. Why Other Options Are Wrong: Boundary scan / bed-of-nails: Test methodologies, not logic devices. CLB: A functional block inside an FPGA, not the overall device class. Structured ASIC: Different category using prefabricated arrays customized by metal layers. Common Pitfalls: Confusing CPLDs with small FPGAs; assuming LUT-centric architecture; overlooking nonvolatile configuration and deterministic timing advantages. Final Answer: CPLD

Question 19

Family resemblance: The GAL16V8 architecture is most similar to which earlier programmable logic device family?

Accepted Answer

Introduction / Context: GAL (Generic Array Logic) devices were introduced as reprogrammable, pin-compatible upgrades to popular PAL parts. Recognizing this lineage helps when replacing obsolete PALs in legacy designs. Given Data / Assumptions: Part referenced: GAL16V8. PAL devices used a programmable AND array and fixed OR array. GALs maintain similar macrocell structures but allow reprogramming. Concept / Approach: The GAL16V8 mirrors the PAL16V8’s I/O architecture and macrocell style, enabling drop-in replacement in many circuits. PROMs and PLAs have different internal organizations (PROM: fixed decoder with programmable outputs; PLA: both arrays programmable). Step-by-Step Solution: Identify GAL as a PAL-compatible technology with EEPROM cells.Note pin/function compatibility with popular PAL packages.Conclude the closest match is the PAL family. Verification / Alternative check: Datasheets list PAL-to-GAL migration guidance, including macrocell modes (combinational/registered) and output enable behavior. Why Other Options Are Wrong: PROM: Memory-oriented, different internal structure. PLD/SPLD (generic): True categories, but the question asks for the most similar specific family. PLA: Both arrays programmable, unlike PAL/GAL pairing. Common Pitfalls: Assuming all SPLDs are interchangeable; ignoring pin-compatibility and macrocell mode details when substituting parts. Final Answer: PAL

Question 20

Historical classification: “The field-programmable logic array (FPLA) was the first ________ programmable logic device.” Select the best completion.

Accepted Answer

Introduction / Context: Early programmable logic evolved from memory-derived approaches (e.g., PROMs used as look-up tables) to dedicated logic arrays. The FPLA marked a shift toward devices architected for logic implementation rather than simply repurposing memory structures. Given Data / Assumptions: “Nonmemory” here contrasts with PLD implementations derived from memory arrays. FPLA provided programmable AND and OR arrays to realize logic directly. We seek the historical descriptor distinguishing FPLA from memory-based devices. Concept / Approach: Before PLAs/PLDs, PROMs were commonly used to implement logic via stored truth tables—fundamentally a memory technique. FPLAs provided a logic-centric fabric (programmable logic arrays) rather than a memory look-up, making them the first prominent nonmemory PLDs in common classification schemes. Step-by-Step Solution: Identify that “logic array” is generic and does not capture the contrast with memory-based PLDs.Recognize the taxonomy: memory-based vs. nonmemory PLDs.Choose “nonmemory” as the historically meaningful completion. Verification / Alternative check: Textbook timelines position PROM-based logic as precursors, followed by PLAs/FPLAs that implemented Boolean equations directly using programmable gate arrays, not addressable memory words. Why Other Options Are Wrong: Understandable / multifunction: Vague and not historically used descriptors. Logic array: Tautological; FPLA already stands for logic array. Mask-programmed: Opposite of “field-programmable.” Common Pitfalls: Confusing “field-programmable” with “nonvolatile”; mixing up FPLA with PLA or PAL; assuming all early PLDs were memory-derived. Final Answer: nonmemory

Programmable Logic Device Questions