Question 1

FPGA terminology — CLB expansion In field-programmable logic device documentation, the acronym CLB most commonly stands for:

Accepted Answer

Introduction / Context: Vendors use a consistent set of acronyms to describe major building blocks in an FPGA architecture. Recognizing these acronyms is key to reading datasheets, understanding resource counts, and mapping HDL logic to hardware. CLB is one of the most ubiquitous terms in the FPGA world. Given Data / Assumptions: We refer to general FPGA documentation (e.g., Xilinx families) where CLB is a standard term. CLBs contain LUTs, flip-flops, carry chains, and routing to implement logic functions. Other options (buffers) are not standard expansions of CLB. Concept / Approach: “Configurable Logic Block” is the canonical expansion of CLB. A CLB groups smaller primitives (LUTs and registers) into a tile that can be configured to perform a wide range of combinational and sequential functions, often with fast carry logic and local routing. Step-by-Step Solution: Identify standard vendor nomenclature.Recall that CLB includes multiple logic resources and interconnect.Select “Configurable Logic Block.” Verification / Alternative check: Review block diagrams for common FPGA families: CLBs are the tile repeated throughout the fabric, sitting between global routing channels. Why Other Options Are Wrong: “Buffer” variants do not match literature; buffers are specific I/O or routing elements, not the main logic tile. “Critical” or “Constant” are not part of the standard acronym. Common Pitfalls: Confusing CLB (a logic tile) with slices or logic cells (subdivisions within a CLB). Different families may group resources differently but keep the CLB name. Final Answer: Configurable Logic Block

Question 2

Comparing GAL22V10 and GAL16V8 capabilities What capability does a GAL22V10 offer that a GAL16V8 does not, assuming classic GAL device families and configurations?

Accepted Answer

Introduction / Context: Within GAL families, parts differ in input width, macrocell count, and the number of special-function pins (SFPs) that provide global set/reset, global output enable, or dedicated clocking. Knowing these differences helps choose the right device when you need more flexible pin functions or additional registers. Given Data / Assumptions: GAL16V8: 16 inputs feeding the array and 8 macrocells/outputs. GAL22V10: 22 inputs feeding the array and 10 macrocells/outputs. Classic GALs are erasable/reprogrammable but typically not “in-system programmable” in the modern JTAG sense (unless specific LV/ISP variants are used). Concept / Approach: The GAL22V10 provides more macrocells and typically a greater number of special-function pins compared to the GAL16V8, enabling additional global controls and flexible pin assignments. While some later derivatives introduced ISP features, the generic comparison between baseline GAL16V8 and GAL22V10 focuses on resource counts and SFP availability rather than ISP capability. Step-by-Step Solution: List resource differences: 22V10 has more inputs and macrocells than 16V8.Identify that 22V10 families usually expose more SFPs (e.g., extra global OE/CLK).Conclude that “twice the special function pins” is the distinguishing capability among the provided options. Verification / Alternative check: Datasheets and selection guides show expanded SFP support and macrocell counts for 22V10 over 16V8, aligning with broader pinout and function capability. Why Other Options Are Wrong: “Extra-large array” is vague and not a standard marketing differentiator here. “In-system programmable” is not generally true for classic GAL vs GAL; ISP is a feature of specific sub-families, not the baseline part. “All of the above” fails because not all claims are universally correct. Common Pitfalls: Assuming every GAL22V10 is ISP; many require external programmers, just like GAL16V8. Final Answer: It has twice the special function pins.

Question 3

MAX7000S tri-state control options For Altera (Intel) MAX7000S family CPLDs, how is a tri-state output buffer typically controlled?

Accepted Answer

Introduction / Context: CPLD families like MAX7000S allow flexible output enable (OE) control for each I/O macrocell. Designers may need constant drive, globally gated outputs for bus sharing, or context-sensitive enables derived from logic in other macrocells. Recognizing all supported control modes is essential when planning board-level bus architectures. Given Data / Assumptions: Each macrocell output buffer includes an OE control path. Global OE pins can gate many outputs simultaneously. OE can also be driven by internal logic equations from other macrocells. Static configuration can permanently enable or disable a buffer in some modes. Concept / Approach: MAX-class CPLDs expose several OE sources: fixed (always on/off), global OE signals, or a product-term/logic-driven OE. This mix supports simple point-to-point signals, multiplexed buses, and time-shared resources using deterministic, low-skew control. Step-by-Step Solution: Identify static OE modes: permanently enabled/disabled for dedicated outputs.Identify global OE gating: tie OE to one of the device’s global OE pins.Identify logic-driven OE: derive from other macrocells or product-term equations.Therefore, the correct choice is “All of the above.” Verification / Alternative check: Device handbooks show OE selection multiplexers with choices including global signals and product-term-based enables; some fitter options permit fixed enable states. Why Other Options Are Wrong: Each single choice describes only one valid mode; the family supports all of them. Common Pitfalls: Forgetting active-low vs active-high OE polarity; overlooking bus-hold and slew-rate settings that also affect system behavior. Final Answer: All of the above

Question 4

What is a “slice” in programmable logic architecture? In common FPGA documentation, a slice typically consists of:

Accepted Answer

Introduction / Context: Architectural terminology varies slightly across generations, but many mainstream FPGA families organize logic into CLBs, each of which may be subdivided into “slices.” Understanding the typical content of a slice helps you reason about how synthesis tools pack LUTs and registers and how many resources are available per tile of the fabric. Given Data / Assumptions: Classic slice definitions (e.g., earlier Xilinx families) describe a slice as containing two logic cells. A logic cell generally includes one LUT plus an associated flip-flop and carry/fast local interconnect. Newer families may vary, but the textbook answer reflects the common baseline definition. Concept / Approach: Historically, a CLB contained two slices, and each slice contained two logic cells, for a total of four cells per CLB. Although modern devices sometimes expand these counts, many educational resources and exam questions use the “two logic cells per slice” convention as the standard reference point. Step-by-Step Solution: Recall baseline organization: CLB → slices → logic cells.Identify that a slice typically holds two logic cells.Therefore, choose “only two logic cells.” Verification / Alternative check: Legacy family datasheets and training material show block diagrams where each slice has two LUT+FF pairs, sometimes with additional distributed RAM/shift register modes. Why Other Options Are Wrong: “Between 2 and 8,” “up to 16,” and “a single CLB” do not reflect the widely taught baseline; a CLB is larger than a slice, not equal to it. Common Pitfalls: Applying a specific modern family’s terminology (e.g., slices with four 6-LUTs) to general exam questions. Always align with the conventional definition unless a specific family is stated. Final Answer: only two logic cells

Question 5

GAL16V8 device pin capabilities — identify the configurable I/O pins In the standard 20-pin GAL16V8 (Generic Array Logic) device used in digital design, which statement correctly describes its pin capabilities?

Accepted Answer

Introduction / Context: The GAL16V8 is a popular small programmable logic device used to implement glue logic, state machines, and decoders. Understanding its pinout and which pins are fixed versus configurable is foundational when replacing multiple SSI/MSI gates with a single PLD on a PCB. Given Data / Assumptions: Package: typically 20 pins with VCC and GND fixed. One side of the device provides dedicated inputs. The opposite side presents eight configurable macrocells that can function as outputs or as additional inputs, depending on the chosen mode. Concept / Approach: GAL16V8 devices combine a programmable AND array with macrocells that can be configured per pin. The classic allocation is eight dedicated input pins (often on the left side) and eight configurable I/O macrocells (often on the right side). Therefore, the correct characterization is that there are eight pins that can be used as inputs or outputs depending on the JEDEC configuration and design constraints. Step-by-Step Solution: Identify fixed resources: power pins and certain control pins are fixed-function.Count dedicated inputs: eight pins are input-only in common operating modes.Count configurable macrocells: eight pins may act as outputs (with optional registered/comb modes) or be configured as inputs.Conclude that “8 pins that are used as inputs or outputs” correctly describes the GAL16V8. Verification / Alternative check: Typical datasheets enumerate pins 2–9 as dedicated inputs and pins 12–19 as I/O macrocells. Mode tables (e.g., Simple, Complex, Registered) control whether a macrocell acts as a combinational or registered output or is folded back as an input to the array. Why Other Options Are Wrong: 16 dedicated inputs: contradicts the macrocell I/O capability. “8 special function pins”: vague and not the standard description. “All of the above”: cannot be true given (a) is false. “8 dedicated outputs only”: ignores input-capable macrocell modes. Common Pitfalls: Assuming every right-side pin must be an output; many designs legally configure them as inputs. Final Answer: 8 pins that are used as inputs or outputs.

Question 6

Acronym expansion in programmable logic — “GAL” stands for what? In the context of PAL/GAL devices used for glue logic and small combinational designs, expand the acronym “GAL”.

Accepted Answer

Introduction / Context: PALs (Programmable Array Logic) and GALs (Generic Array Logic) are classic small programmable logic devices used to replace multiple fixed SSI/MSI gates. Knowing the correct expansion of common acronyms prevents confusion when reading datasheets, app notes, and historical documentation in digital design courses and labs. Given Data / Assumptions: The term GAL is specific to reprogrammable PAL-like devices. Vendors produced GALs as pin-compatible upgrades to older PALs. “Generic” refers to their general-purpose applicability across many logic functions. Concept / Approach: Manufacturers introduced GALs as a more flexible, electrically erasable alternative to one-time programmable PALs. Hence the naming emphasizes “Generic” capability rather than “Programmable” in the acronym itself. GAL devices keep the same basic AND-OR product-term architecture while allowing multiple reprogramming cycles. Step-by-Step Clarification: Break down letters: G → Generic, A → Array, L → Logic.Relate to function: a generic programmable array implementing logic via product terms.Confirm usage: textbooks and datasheets consistently define GAL as “Generic Array Logic.” Verification / Alternative check: Device markings and family names (e.g., GAL16V8, GAL22V10) in vendor literature explicitly expand to Generic Array Logic. The architectural descriptions match PAL-like devices with reprogrammable technology (e.g., EEPROM/flash) instead of fuse-only arrays. Why Other Options Are Wrong: General/Giant/Generic Analysis: these phrases are not used in industry nomenclature for GAL devices. Global Arithmetic Logic: conflates with ALU terminology, irrelevant here. Common Pitfalls: Confusing GAL with FPGA “LUT” terminology; they are different device classes and eras. Final Answer: Generic Array Logic

Question 7

Macrocell contents in PAL/GAL/CPLD architecture — what does a macrocell include? In programmable logic devices, a macrocell is the per-output logic unit. Which description best captures what a macrocell basically contains?

Accepted Answer

Introduction / Context: Macrocells are the fundamental building blocks of many SPLDs and CPLDs. Each macrocell typically feeds an external pin and can be configured for combinational or registered operation. Understanding what is inside a macrocell helps designers map Boolean equations, state machines, and output enables correctly. Given Data / Assumptions: Classic PAL/GAL/CPLD architecture uses a programmable AND array generating product terms. Product terms are summed in an OR structure for each output macrocell. Optional output features often include an XOR for polarity, a register (flip-flop), and an output enable control. Concept / Approach: At its core, the macrocell realizes sum-of-products logic. A set of programmable AND gates form minterms (product terms). These feed an OR function to produce the desired equation, which can then be optionally registered and sent through an output buffer with tri-state control. Thus, “an AND-OR gate array and some output logic” is the best concise description. Step-by-Step Reasoning: Identify inputs: device pins and feedbacks feed the AND array.Generate product terms in the programmable AND plane.Sum product terms via the OR function dedicated to each macrocell.Optionally register and buffer the result to the output pin (and feedback path). Verification / Alternative check: Block diagrams in vendor datasheets label a macrocell as AND/OR logic plus an optional D-type flip-flop, XOR for polarity, and tri-state output buffer. No “licensed programming” or input-buffer-only description is used. Why Other Options Are Wrong: “Programmable AND-OR and some input buffers”: focuses on inputs; macrocells drive outputs. “OR-gate array and some output logic”: ignores the crucial programmable AND plane. “Licensed programming”: unrelated to architecture. “Only a D flip-flop”: incomplete; combinational plane is essential. Common Pitfalls: Assuming macrocells are only registers; many are used purely combinationally. Final Answer: an AND-OR gate array and some output logic

Question 8

Product terms in PLDs — which gate produces them? Inside a PAL/GAL/CPLD logic array that implements sum-of-products, the signals known as “product terms” are the outputs of what kind of gate?

Accepted Answer

Introduction / Context: Programmable logic devices often realize Boolean functions using the sum-of-products form. In this style, “product terms” and “sum terms” refer to intermediate signals inside the logic plane. Knowing which gates generate these signals clarifies how equations map onto hardware resources like macrocells and product term allocators. Given Data / Assumptions: Sum-of-products means OR of ANDs (e.g., F = AB + CD). PLDs feature a programmable AND plane followed by an OR function per output macrocell. Signals may be available in both true and complemented forms to the AND plane. Concept / Approach: Each “product term” corresponds to the logical product (AND) of a selected set of literals (variable or its complement). The programmable connections into the AND plane define which literals are included. The outputs of these AND gates are then ORed to form the final logic equation for a given macrocell output. Step-by-Step Reasoning: Choose literals (A, Ā, B, B̄, …) via fuses or EEPROM links.The AND gate combines the chosen literals to yield a product term (e.g., ABC̄).Several product terms are then fed into an OR to create the output function. Verification / Alternative check: Block diagrams of PAL/GAL devices label the first stage as a programmable AND array producing product terms, confirming the terminology used in textbooks and datasheets. Why Other Options Are Wrong: OR/XOR/NOR: these are used elsewhere (summing, polarity), not for forming product terms. Flip-flop: sequential storage, not combinational product generation. Common Pitfalls: Confusing “product term” with “sum term”; sum terms arise from ORing product terms. Final Answer: AND

Question 9

Combinational logic via stored tables — identify the circuit type A circuit that implements a combinational logic function by storing a complete table of output values for every possible input combination is called a:

Accepted Answer

Introduction / Context: Modern FPGAs and some CPLDs use small memories to realize arbitrary combinational logic. These memories are programmed with the desired output for each input address. The concept is foundational for understanding how synthesis maps Boolean functions onto physical resources in programmable devices. Given Data / Assumptions: A k-input combinational function has 2^k possible input combinations. Each combination maps to a single output bit (or bits). The device provides a small RAM/ROM-like element that is preloaded with these bits. Concept / Approach: By treating the inputs as address lines into a tiny memory and storing the desired output bit at each address, the device directly implements the truth table. This memory-based implementation is called a look-up table (LUT). LUTs are universal combinational primitives because any Boolean function of k variables can be expressed this way. Step-by-Step Reasoning: Enumerate inputs → 2^k addresses.Assign each address a stored bit equal to the intended function value.During operation, current inputs select an address and the stored bit emerges as the output.Thus, the circuit is a LUT implementing the function. Verification / Alternative check: FPGA vendor docs show LUTs implemented as SRAM bits driving a multiplexer tree. This hardware behaves identically to a precomputed truth table indexed by inputs. Why Other Options Are Wrong: Output logic macrocell/logic element: broader architectural terms; the specific truth-table device is a LUT. Parallel logic expander: not a standard term for truth-table realization. Programmable counter: sequential device, not purely combinational. Common Pitfalls: Confusing LUTs (combinational) with registers or block RAMs (sequential/storage). Final Answer: look-up table

Question 10

Vendor architectures — PAL vs. PLA in classic CPLDs Which statement correctly matches the traditional internal array style associated with Altera and Xilinx CPLD families?

Accepted Answer

Introduction / Context: Classic CPLDs from major vendors historically differed in their internal product-term array structures. “PAL” generally denotes a programmable AND array feeding a fixed OR array, while “PLA” denotes both AND and OR arrays being programmable. Recognizing these differences helps interpret how equations map to silicon resources and why product-term allocation behaves differently across families. Given Data / Assumptions: Altera MAX-series CPLDs historically favored PLA-like flexibility. Xilinx XC9500-series CPLDs are commonly described as PAL-like product-term devices. Both vendors also offer FPGA families that use LUTs (a different architecture). Concept / Approach: In a PLA-style device, both planes (AND and OR) are programmable, offering more freedom in assigning product terms to outputs. In PAL-style devices, the OR plane is more constrained (fixed), which can simplify timing at the cost of flexibility. The common textbook matching is Altera → PLA-like, Xilinx → PAL-like for their classic CPLD lines. Step-by-Step Reasoning: Define architectures: PAL = programmable AND + fixed OR; PLA = programmable AND + programmable OR.Associate vendors: Altera CPLDs → PLA-like; Xilinx CPLDs → PAL-like.Therefore, the correct pairing is “Altera uses PLA and Xilinx uses PAL.” Verification / Alternative check: Vendor application notes and many digital design textbooks describe Altera MAX devices with flexible product-term sharing (PLA-like) and Xilinx XC9500 with fixed product-term allocations per macrocell (PAL-like), which aligns with the selected answer. Why Other Options Are Wrong: Swapped or “both same” statements contradict widely cited architectural descriptions. “LUT-only” applies to mainstream FPGAs, not to classic product-term CPLDs. Common Pitfalls: Assuming all programmable logic uses LUTs; CPLDs are product-term devices. Final Answer: Altera uses PLA architecture and Xilinx uses PAL architecture.

Question 11

Relationship between PAL and GAL — what is a GAL essentially? Choose the statement that best describes what a GAL device is, relative to a traditional PAL.

Accepted Answer

Introduction / Context: PALs (Programmable Array Logic) were historically one-time programmable using fuse technology. GALs (Generic Array Logic) were introduced as a drop-in, electrically erasable alternative, allowing designers to iterate on designs without replacing devices, thereby reducing cost and development time. Given Data / Assumptions: PAL: OTP (one-time programmable) fuse-based technology in many classic parts. GAL: EEPROM/flash-based reprogrammable technology with PAL-compatible pinouts. Both are product-term devices using AND/OR macrocells. Concept / Approach: The architectural similarity between PALs and GALs is strong—both implement sum-of-products logic. The key distinction is reprogrammability: GALs can be erased and reprogrammed many times. Therefore, the most accurate short description of a GAL is “a reprogrammable PAL.” Step-by-Step Clarification: Identify PAL limitations: OTP fuses prevent changes after programming.Identify GAL capability: erasable (electrically), enabling multiple design cycles.Conclude: GALs serve as pin-compatible, reprogrammable successors to PALs. Verification / Alternative check: Family names like GAL16V8 and GAL22V10 mirror PAL part codes (16V8, 22V10) and vendor literature promotes them as reprogrammable replacements, confirming the relationship. Why Other Options Are Wrong: Non-reprogrammable/manufacturer-programmed: describes OTP parts, not GALs. “Very large PAL”: GALs match similar densities; “very large” is misleading. “Only tri-state buffers”: incorrect; macrocells and product terms are present. Common Pitfalls: Assuming GALs imply higher logic capacity; the main differentiation is erasability and flexibility. Final Answer: reprogrammable PAL

Question 12

Input protection in PAL/GAL devices — preventing loading of the AND array At the inputs of PAL/GAL devices, what component is commonly used to prevent excessive loading from driving a large number of AND-plane connections?

Accepted Answer

Introduction / Context: In product-term devices such as PALs and GALs, each input signal may feed many programmable connections in the AND plane. Without proper input buffering, the fan-out and capacitive loading could degrade signal integrity and timing. Devices therefore include input buffers to isolate the external pin from the internal array loading. Given Data / Assumptions: Inputs often drive both true and complemented forms into the AND array. The AND array can present significant capacitive load due to many programmable links. Signal integrity and timing must be preserved across temperature and voltage. Concept / Approach: An input buffer provides strong, well-controlled drive, proper logic thresholds, and isolation from internal loading. By placing a buffer between the external pin and the array, the device ensures predictable propagation delay and reduces the risk of waveform distortion, ringing, or slow edges that could violate setup/hold timing for internal registers. Step-by-Step Reasoning: External input → CMOS/TTL buffer at the pin.Buffered signal (and its complement via an internal inverter) fans out into the AND plane.Programmable connections select which literals drive product terms without burdening the outside world with the load. Verification / Alternative check: Vendor block diagrams show input buffers feeding both true and complement lines into the programmable array, which then connect to many product terms as needed. Why Other Options Are Wrong: Simplified AND gates/fuses: relate to array programmability, not input isolation. Latches: provide storage, not load isolation. LEDs: irrelevant to input conditioning. Common Pitfalls: Underestimating the effect of capacitive loading on rise/fall times when many product terms tap a signal. Final Answer: Buffers

Question 13

Device families and classification SPLDs (simple PLDs), CPLDs (complex PLDs), and FPGAs (field-programmable gate arrays) all belong to which broader class of reconfigurable digital devices?

Accepted Answer

Introduction / Context: This question checks your understanding of how common reconfigurable logic device families are categorized. Knowing the umbrella term for SPLDs, CPLDs, and FPGAs helps you navigate datasheets, select parts, and communicate architecture choices in digital design projects. Given Data / Assumptions: SPLD stands for simple programmable logic device. CPLD stands for complex programmable logic device. FPGA stands for field-programmable gate array. We are classifying these by device type, not by the specific programming technology (for example, EEPROM, SRAM, antifuse). Concept / Approach: All three device classes allow the user to implement custom logic functions after manufacturing. The collective term used in textbooks and vendor literature is PLD, which stands for programmable logic device. PAL (programmable array logic) is a type of SPLD. EPROM and SRAM describe memory technologies, not device classes, even though some PLDs may internally use those technologies to store configuration. Step-by-Step Solution: Identify the common characteristic: user-programmable logic.Recognize the umbrella category that includes SPLD, CPLD, and FPGA → PLD.Eliminate answers that are either subtypes (PAL) or unrelated memory tech (EPROM, SRAM).Choose PLD as the correct classification. Verification / Alternative check: Check any vendor overview: product lines are typically organized into SPLDs, CPLDs, and FPGAs under the broader heading of PLDs, confirming the classification. Why Other Options Are Wrong: PAL: A specific SPLD architecture, not the umbrella category. EPROM / SRAM: Memory technologies used to store data or configuration, not device families themselves. Common Pitfalls: Confusing device class (PLD) with configuration technology (for example, EEPROM or SRAM). Another mistake is assuming PAL equals all PLDs; PAL is only one historical variant. Final Answer: PLD

Question 14

Definition check What does the acronym PROM stand for in digital electronics?

Accepted Answer

Introduction / Context: PROM is a foundational nonvolatile memory component used to store fixed data such as lookup tables and firmware. Understanding the definition distinguishes memory devices from programmable logic devices (PLDs) like CPLDs and FPGAs, which implement arbitrary logic rather than just storing data patterns. Given Data / Assumptions: PROM is a memory device acronym encountered in digital systems courses and datasheets. We seek the full expansion and meaning of the acronym. No vendor-specific nuance is required; standard textbook definition applies. Concept / Approach: PROM expands to Programmable Read-Only Memory. It is manufactured blank and then permanently programmed once (for example, by burning fuses). Variants include EPROM (erasable with ultraviolet light), EEPROM/Flash (electrically erasable). PROM is not a PLD; it stores data rather than configurable gate interconnects. Its output is determined solely by address inputs, not by combinational networks synthesized from HDL. Step-by-Step Solution: Break down the acronym: P = Programmable, R = Read, O = Only, M = Memory.Recall typical usage: fixed tables, microcode, device IDs.Differentiate from PLD/FPGA (which implement logic networks).Select the option that exactly states Programmable Read-Only Memory. Verification / Alternative check: Introductory digital design texts define PROM as a one-time programmable nonvolatile memory, confirming the expansion and meaning. Why Other Options Are Wrong: Programmable Logic Device: A broader class (PLD), not a memory acronym. Polarized Readout Module / Peripheral Register and Output Matrix: Fabricated distractors, not standard terminology. Common Pitfalls: Assuming all programmable devices implement logic (confusing PROM with PLD). PROM stores static data; it does not provide the flexible routing and LUT fabric of FPGAs or the product-term arrays of PALs/GALs. Final Answer: Programmable Read-Only Memory

Question 15

Architectural trade-offs What is the most common performance limitation (major downfall) of microprocessor/DSP-only systems compared to hardware logic like CPLDs/FPGAs?

Accepted Answer

Introduction / Context: Choosing between software running on microprocessors/DSPs and dedicated hardware (CPLDs/FPGAs/ASICs) is a core architecture decision. While software offers rapid iteration and rich libraries, some applications require deterministic, ultra-low-latency or high-throughput processing that general-purpose CPUs/DSPs struggle to achieve. Given Data / Assumptions: We compare sequential instruction execution (µP/DSP) with parallel hardware implementations (CPLD/FPGA). Target workloads include high-speed control, packet processing, and signal processing at line rates. We ignore specialized accelerators or heterogeneous SoCs for this basic comparison. Concept / Approach: Microprocessors and many DSPs execute instructions sequentially (or in limited superscalar/parallel forms), whereas FPGAs exploit deep spatial parallelism. For tight timing loops, nanosecond-class I/O handshakes, or massive multiply-accumulate arrays, custom logic pipelines reach far higher deterministic speed with lower latency. Thus, the common limitation of software-only solutions is inadequate speed for demanding real-time tasks. Step-by-Step Solution: Identify workload requiring concurrent operations (for example, multiple filters, parallel protocol checks).Note that CPUs/DSPs serialize or partially parallelize; FPGAs instantiate many operations concurrently.Throughput scales with clock and parallel instances in hardware; software mostly scales with clock and instruction-level parallelism.Conclude that speed—insufficient for stringent tasks—is the major shortcoming of µP/DSP-only designs. Verification / Alternative check: Latency measurements routinely show sub-microsecond responses in FPGA logic versus millisecond or tens of microseconds for software stacks, supporting the speed argument in real deployments. Why Other Options Are Wrong: Too fast: Nonsensical as a “downfall.” Too much/Not enough flexibility: Flexibility is a strength of software; the common pain point is not flexibility but performance. Common Pitfalls: Overlooking memory and I/O bottlenecks that further slow software solutions; ignoring determinism requirements (jitter) that hardware meets more easily than software on multitasking systems. Final Answer: Speed—they are too slow

Question 16

GAL22V10 device pins (clarified) Which statement correctly summarizes the GAL22V10 pin configuration for user I/O and special pins?

Accepted Answer

Introduction / Context: The GAL22V10 is a classic CMOS GAL (Generic Array Logic) device widely used for glue logic. Understanding its pinout is essential when replacing older PALs or migrating designs, because available inputs, I/Os, and special-purpose pins determine what logic can be packed into a single device. Given Data / Assumptions: Package: 24 pins (typical DIP/PLCC/SOIC variants). Ten macrocells provide outputs with feedback (configurable features per macrocell). Dedicated inputs supply product terms into the AND array. Two special pins: a global clock and an output enable/control. Concept / Approach: Device naming “22V10” hints at available resources: up to 22 inputs (including feedback) and 10 outputs (macrocells). Practically, pinout summaries list 10 I/O macrocells, 12 dedicated input pins, and 2 special function pins (often CLK and OE). These signals flow into the internal programmable AND array and fixed OR structure, with macrocells at the outputs for optional registering and tri-state control. Step-by-Step Solution: Identify macrocell count: 10 outputs that may feed back internally.Count dedicated inputs: 12 pins that only act as inputs.Account for special-purpose pins: 2 pins (typical roles are global CLK and OE).Confirm these add to 24 pins appropriate for the package family. Verification / Alternative check: Typical datasheets/tabular pin lists show 10 I/O macrocells and 12 inputs, plus CLK and OE or equivalent control pins, aligning with the correct option. Why Other Options Are Wrong: No special pins: Contradicts the presence of global control pins. 8 configurable I/O: Confuses GAL22V10 with GAL16V8. 22 outputs and 10 inputs: Inverts the meaning of 22V10 and contradicts the physical pin count. Common Pitfalls: Assuming all “22” pins are dedicated inputs (several are macrocell I/O) or overlooking feedback paths that let outputs act as inputs to logic. Final Answer: 10 output macrocells (I/O), 12 dedicated input pins, plus 2 special-purpose pins (CLK and OE)

Question 17

Acronym expansion FPGA is the standard acronym for what class of reconfigurable devices?

Accepted Answer

Introduction / Context: Expanding common acronyms is essential when reading datasheets, application notes, and research papers. FPGA is among the most widely used terms in digital design and embedded systems, representing a dominant platform for prototyping and production logic. Given Data / Assumptions: The acronym FPGA appears in the context of programmable logic. We assume standard industry usage with no vendor-specific rebranding. Concept / Approach: FPGA expands to Field Programmable Gate Array. “Field programmable” means the device can be configured by the end user (in the field) rather than only at the factory. “Gate array” references the array of configurable logic (for example, LUTs and routing resources) that collectively implements digital circuits defined by an HDL bitstream. Step-by-Step Solution: Recall: F = Field, P = Programmable, G = Gate, A = Array.Relate to functionality: arrays of configurable logic blocks and routing.Confirm no alternative expansions are accepted in standard literature.Select “Field Programmable Gate Array.” Verification / Alternative check: Vendor documentation (for example, Xilinx, Intel/Altera) consistently expands FPGA as Field Programmable Gate Array. Why Other Options Are Wrong: Generic Array / Programmer's Gate Assembly: Not industry standards. Flexible Programming [of] Generic Assemblies: Worded to mislead; not used in electronics. Common Pitfalls: Confusing FPGA with CPLD (complex programmable logic device); although related, the architectures and best-fit applications differ. Final Answer: Field Programmable Gate Array

Question 18

GAL16V8 OLMC composition Within a GAL16V8 device, which of the following is not a named functional mux associated with the Output Logic Macrocell (OLMC)?

Accepted Answer

Introduction / Context: GAL16V8 devices contain Output Logic Macrocells (OLMCs) that provide options such as registered vs. combinational output, output enable control, inversion, and feedback routing. Understanding the named blocks around the OLMC helps when reading vendor diagrams and timing paths. Given Data / Assumptions: Typical OLMC blocks include an Output MUX (OMUX), Feedback MUX (FMUX), and Tri-State/Output Enable MUX (often shown as TSMUX). Naming conventions are consistent in many datasheets, though minor variations exist. We identify which acronym is not standard for the OLMC. Concept / Approach: The OLMC takes the sum-of-products signal from the OR array and conditions it through selectable elements. The OMUX chooses the data path (for example, registered/combination). The FMUX selects what is fed back to the AND array. The TSMUX (tri-state mux) or equivalent controls output enable behavior. “PSMUX” (product-term select mux) is not a commonly labeled OLMC block; product-term selection is handled in the AND/OR arrays rather than by a named PSMUX within the OLMC. Step-by-Step Solution: List standard OLMC multiplexers: OMUX, FMUX, TSMUX.Note where product-term selection occurs: in the array, not an OLMC “PSMUX.”Match acronyms to functions: output, feedback, tri-state enable.Conclude PSMUX is the non-standard/incorrect element. Verification / Alternative check: Block diagrams in vendor application notes (for example, GAL16V8) show OMUX/FMUX/TS control but no PSMUX label at the OLMC boundary. Why Other Options Are Wrong: TSMUX: Controls three-state/enable behavior at the output. OMUX: Selects between registered/combinatorial or alternate data sources. FMUX: Routes feedback from the macrocell back into the logic array. Common Pitfalls: Assuming naming uniformity across all vendors; focus on the functional roles, which persist despite minor label differences. Final Answer: PSMUX

Question 19

MAX7000 family basics In the Altera/Intel MAX7000 family, how many macrocells does a single LAB (Logic Array Block) contain?

Accepted Answer

Introduction / Context: Understanding the granular resources of CPLD families like MAX7000 helps with capacity planning, fitting, and timing. The LAB (Logic Array Block) is a fundamental grouping unit in these devices, containing a fixed number of macrocells that share product terms and routing resources. Given Data / Assumptions: MAX7000 devices are EEPROM-based CPLDs with macrocells grouped into LABs. Design tools report resource usage in macrocells and LABs. We are focusing on the standard LAB composition for the MAX7000 family. Concept / Approach: In MAX7000-class devices, each LAB contains 16 macrocells. A macrocell typically includes a register (flip-flop), product-term allocator, and output control allowing registered or combinational operation. Knowing “16 per LAB” lets you quickly estimate how many LABs your equations will occupy given a macrocell count, and whether cross-LAB product-term routing might be required. Step-by-Step Solution: Recall MAX7000 architecture: EEPROM configuration with LAB-based organization.Remember the standard per-LAB macrocell count: 16.Use this figure for early sizing (for example, a 128-macrocell design needs about 8 LABs).Consider fit implications (product-term sharing and pin/IOB constraints) beyond raw counts. Verification / Alternative check: Architecture overviews and datasheets consistently show 16 macrocells per LAB in MAX7000 series CPLDs. Why Other Options Are Wrong: 8/32/64: Do not match the MAX7000 LAB organization; these numbers are typical of other device families or different grouping constructs. Common Pitfalls: Assuming FPGA-style LAB/CLB counts map directly to CPLDs; CPLDs use product-term logic with different packing behavior compared to LUT-based FPGAs. Final Answer: 16

Question 20

Reprogrammability of GAL devices Approximately how many erase/reprogram cycles can typical GAL devices withstand over their lifetime?

Accepted Answer

Introduction / Context: GALs (Generic Array Logic) are electrically erasable and reprogrammable, making them convenient for iterative development and field updates. Understanding endurance helps plan maintenance and ensures reliability in manufacturing where devices may be reprogrammed multiple times during testing and updates. Given Data / Assumptions: We refer to typical commercial GAL16V8/20V8/22V10 devices. Endurance is specified in datasheets as a minimum guaranteed number of erase/write cycles. Actual endurance may exceed the guaranteed minimum in many parts. Concept / Approach: GALs use EEPROM/Flash-like technologies for configuration storage. Vendors commonly rate endurance at or above 10,000 cycles. While earlier technologies (for example, UV-erasable EPROM) required exposure to UV light and had different constraints, GALs can be electrically erased and rewritten many times, supporting robust iterative workflows. Step-by-Step Solution: Identify the storage technology used in GALs (electrically erasable).Recall typical endurance ratings from datasheets (often 10^4 cycles or more).Choose the option that reflects “Over 10,000” cycles.Note that environmental factors (temperature, voltage) can affect lifetime; always consult the specific part's datasheet. Verification / Alternative check: Manufacturer specifications for popular GALs list endurance around 10,000 program/erase cycles minimum, confirming the selection. Why Other Options Are Wrong: 0: Contradicts reprogrammable nature. At least 100 / At least 1000: Understate modern device endurance by orders of magnitude. Common Pitfalls: Confusing GALs with one-time programmable PALs; not accounting for data retention limits (for example, 10+ years) which are separate from cycle endurance. Final Answer: Over 10,000

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