Question 1

Boolean notation refresher: in Boolean algebra, an overbar denotes the NOT operation. The plus sign corresponds to which logical operation?

Accepted Answer

Introduction / Context: Boolean algebra uses compact symbols that map directly to logic gates. Remembering these mappings is essential for interpreting expressions and implementing them with gates. Given Data / Assumptions: Overbar indicates NOT (inversion). We must identify the operation indicated by the plus sign. Standard Boolean algebra conventions apply. Concept / Approach: By convention: multiplication (·) means AND, addition (+) means OR, and overbar (¯) means NOT. These symbols simplify algebraic manipulation like distribution, De Morgan’s laws, and minimization. Step-by-Step Solution: Recall symbol set: + → OR, · → AND, ¯ → NOT.Match the question: “plus sign” → OR.Select OR as the answer. Verification / Alternative check: Truth table equivalence: A + B equals 1 when A = 1 or B = 1 (inclusive OR). Why Other Options Are Wrong: AND/NAND/NOR: different operators; NAND/NOR are complements of AND/OR with inversion.None: incorrect because the standard symbol is well established. Common Pitfalls: Confusing inclusive OR with exclusive OR (XOR); XOR is usually denoted by ⊕ or a circled plus. Final Answer: OR

Question 2

Number systems: Convert the binary value 1011011₂ to its decimal (base-10) equivalent. Show the positional weights used.

Accepted Answer

Introduction / Context: Binary-to-decimal conversion reinforces the idea that each bit position represents a power of two. Practicing the expansion method prepares learners for interpreting register contents and memory addresses. Given Data / Assumptions: Binary input: 1011011₂. Bit positions from right (LSB) have weights: 2^0, 2^1, 2^2, ... Unsigned magnitude, no sign bit. Concept / Approach: To convert, multiply each bit by its corresponding power-of-two weight and sum the results. Only positions with bit = 1 contribute to the sum. Step-by-Step Solution: Write weights for 7 bits (MSB→LSB): 64, 32, 16, 8, 4, 2, 1.Match bits 1 0 1 1 0 1 1 → use weights 64, 16, 8, 2, 1.Compute sum: 64 + 16 + 8 + 2 + 1 = 91.Therefore 1011011₂ = 91₁₀. Verification / Alternative check: Convert back by repeated division by 2 on 91 to reconstruct 1011011₂; the remainders match the bit pattern. Why Other Options Are Wrong: 81₁₀, 100₁₀, 200₁₀: these sums do not equal the expansion of the given bit pattern.None of the above: incorrect because 91₁₀ is correct. Common Pitfalls: Misaligning bit weights; forgetting to include both the 2 and 1 contributions at the end. Final Answer: 91₁₀

Question 3

Master–slave JK flip-flop timing: in a JK master-slave configuration, when is the master latch enabled and when does the slave latch update?

Accepted Answer

Introduction / Context: The master–slave JK flip-flop is a classic edge-effective memory element built from two level-sensitive latches. Understanding which latch is active on which clock level explains why the pair behaves like an edge-triggered device and avoids race-through problems. Given Data / Assumptions: Level-sensitive master and slave latches are cascaded. Single clock controls both, with complementary enabling. Positive level enables the master; negative level enables the slave (for the standard convention). Concept / Approach: During the high phase of the clock, the master latch is transparent and can capture changes at J/K (subject to gating). When the clock goes low, the master closes, and the slave latch becomes transparent, taking the master’s stored state to the output, emulating a falling-edge triggered update. Step-by-Step Solution: Clock high → master enabled (transparent), slave disabled.Clock low → master disabled (holds), slave enabled (updates Q).Thus the succinct timing is “high, low.” Verification / Alternative check: Timing diagrams show input sampling while CLK is high and output transfer on the transition to low. This stagger prevents immediate input changes from racing to the output. Why Other Options Are Wrong: set/reset: describe states, not clock levels.race/no change: not a clock-level pairing.set/race: mismatched terms unrelated to clock polarity.None: incorrect because “high, low” is the established description. Common Pitfalls: Confusing master–slave with true edge-triggered FFs; forgetting that implementation details vary with active-high vs. active-low conventions. Final Answer: high, low

Question 4

Spot the error: Which of the following Boolean algebra rules is incorrect under standard Boolean conventions?

Accepted Answer

Introduction / Context: Boolean algebra follows a small set of identities that greatly simplify logic design. Recognizing invalid identities prevents design errors when reducing logic expressions. Given Data / Assumptions: Standard Boolean symbols: + for OR, · for AND, and overbar for NOT. We assume variables are Boolean (0 or 1). We must identify the false identity. Concept / Approach: Key identities include identity, null, idempotent, and dominance laws. The correct forms are: 0 + A = A (identity for OR), 1 + A = 1 (dominance for OR), A + A = A (idempotent), and 1 · A = A (identity for AND). Any deviation from these is incorrect. Step-by-Step Solution: Check 0 + A = A → true (OR identity).Check 1 + A = 1 → true (OR dominance).Check A + A = A → true (idempotent law).Check 1 · x = 1 → false; correct is 1 · x = x (AND identity). Verification / Alternative check: Truth table for 1 · x: when x = 0, 1 · 0 = 0, not 1; when x = 1, 1 · 1 = 1. Therefore the expression equals x, not constant 1. Why Other Options Are Wrong: 0 + A = A: a valid identity.1 + A = 1: a valid dominance law.A + A = A: a valid idempotent law.None of the above: incorrect because one rule is indeed wrong. Common Pitfalls: Confusing dominance vs. identity laws; mixing constant 1 behavior across AND and OR. Final Answer: 1 . x = 1

Question 5

Flowchart notation: In standard flowcharting used for programming logic, arithmetic or other processing operations should be written in which symbol type?

Accepted Answer

Introduction / Context: Flowcharts communicate program logic and system workflows using a small set of standardized symbols. Placing each action in the correct symbol improves readability and prevents misinterpretation during reviews and walkthroughs. Given Data / Assumptions: We are using conventional flowchart symbols. Arithmetic and general data processing statements must be represented. We must choose the correct symbol category. Concept / Approach: The processing symbol (a rectangle) denotes a computational step: calculations, variable assignments, data transformations, or function calls. Decision symbols (diamonds) represent conditional branching; I/O symbols (parallelograms) represent reading or writing; terminal symbols (rounded rectangles/ovals) denote start/end points. Step-by-Step Solution: Identify task: arithmetic/processing.Map to symbol: rectangle → “Process”.Select “Processing symbols.” Verification / Alternative check: Standards and textbooks align on these shapes; many toolkits enforce the same semantics in diagram stencils. Why Other Options Are Wrong: Decision: used for yes/no branching, not computation.Input/Output: for data entry or display/file operations.Terminal: for start/end markers only.None: incorrect because a correct symbol exists. Common Pitfalls: Overusing decision diamonds for multi-way logic instead of combining with processes; writing long pseudo-code inside shapes instead of concise statements. Final Answer: Processing symbols

Question 6

Architecture insight: A master–slave JK flip-flop can be viewed structurally as a cascade of which underlying latch types?

Accepted Answer

Introduction / Context: Understanding how complex flip-flops are built from simpler latches clarifies timing behavior, setup/hold requirements, and why certain race conditions are avoided. The master–slave JK is a pedagogical staple for this reason. Given Data / Assumptions: JK functionality is implemented using level-sensitive latching stages. Master and slave operate on opposite clock levels. Internal gating prevents invalid S=R=1 conditions typical of a basic SR latch. Concept / Approach: The canonical construction uses two gated SR latches in series. The first (master) captures input information while the clock is high; the second (slave) updates the output when the clock is low. Feedback networks around the J and K pins translate JK semantics to valid S and R drive signals for the latches. Step-by-Step Solution: Identify basic building block: gated SR latch.Arrange two latches master→slave with complementary enables.Add gating so J/K requests translate into S/R pulses safely.Conclude structural view: two gated SR latches. Verification / Alternative check: Timing diagrams of the JK master–slave show level transparency phases consistent with SR latch behavior under gating. Why Other Options Are Wrong: SR + T / SR + D / two T / JK + T: none match the standard internal construction. Common Pitfalls: Equating master–slave flip-flops with true edge-triggered designs; overlooking the gating that maps JK inputs to safe SR controls. Final Answer: two gated SR latches (master and slave)

Question 7

Basic terminology check: In number systems and logic, what does the term “binary” literally mean?

Accepted Answer

Introduction / Context: Computers operate on binary representations at every level—logic gates, machine instructions, memory bits. Knowing the literal meaning of “binary” reinforces why only two symbols are needed to encode any information in digital systems. Given Data / Assumptions: “Binary” refers to base-2 representation and two logical states. Common mappings: 0/1, low/high, false/true. Question asks for the literal count implied by the term. Concept / Approach: “Binary” stems from the Latin “bi–” meaning two. The binary number system uses digits 0 and 1, and binary logic uses two stable states. All larger constructs (bytes, words) are compositions of these two states. Step-by-Step Solution: Interpret the word root: “bi” → two.Relate to practice: two symbols in base-2, two logical levels.Select “Two.” Verification / Alternative check: Cross-check with other bases: decimal (“deci” ten) uses ten digits; quaternary uses four; ternary uses three. Why Other Options Are Wrong: Three/Four/Ten: correspond to ternary, quaternary, and decimal respectively.None: incorrect because “Two” is the literal meaning. Common Pitfalls: Confusing the number of symbols with voltage levels; different technologies may invert active-high/active-low but still represent two states. Final Answer: Two

Question 8

Number systems conversion (digital electronics): convert the decimal value 89 (base 10) to its exact binary representation (base 2). Which of the following choices correctly equals 89 in binary?

Accepted Answer

Introduction / Context: Converting between decimal (base 10) and binary (base 2) is a foundational skill in digital electronics and computer architecture. The question asks for the binary representation of 89₁₀. Understanding this helps with addressing, masking, and low-level data manipulations. Given Data / Assumptions: Target value: 89 in base 10. Binary uses powers of 2 (… 64, 32, 16, 8, 4, 2, 1). No sign bit or fractional components are involved. Concept / Approach: The standard approach is repeated subtraction (or division by 2 remainders) using powers of 2. Express 89 as a sum of distinct powers of 2, then place 1s in those bit positions and 0s elsewhere. Highest power of 2 not exceeding 89 is 64 (2^6). Step-by-Step Solution: Identify powers: 89 - 64 = 25 → bit for 2^6 is 1. Next: 25 - 16 = 9 → bit for 2^4 is 1 (2^5 = 32 is too large, so bit 2^5 is 0). Next: 9 - 8 = 1 → bit for 2^3 is 1. Remaining: 1 → bit for 2^0 is 1. Bits for 2^2 and 2^1 are 0. Assemble bits from 2^6 to 2^0: 1 0 1 1 0 0 1 → 1011001₂. Verification / Alternative check: Compute 1011001₂ back to decimal: 64 + 16 + 8 + 1 = 89. This confirms correctness. Why Other Options Are Wrong: 1011011₂ = 64 + 16 + 8 + 2 + 1 = 91 (not 89). 1100111₂ = 64 + 32 + 4 + 2 + 1 = 103 (not 89). 10011₂ = 16 + 2 + 1 = 19 (too small). “None of the above” is incorrect because a correct option exists. Common Pitfalls: Dropping leading zeros is fine, but do not drop necessary middle zeros; confusing the order of bits or mis-summing powers of 2 causes off-by-one errors. Final Answer: 1011001₂

Question 9

Logic family performance comparison: which logic family is generally recognized for the highest switching speed in classic digital design and is therefore used for high-speed applications?

Accepted Answer

Introduction / Context: Digital logic families differ in speed, power consumption, and noise margins. Designers select families appropriate to application needs. Historically, emitter-coupled logic (ECL) is known for top-tier speed due to its non-saturating operation. Given Data / Assumptions: We compare classic logic families: DTL, TTL, ECL, and MOS. Metric of interest: propagation delay (lower is faster). Power and complexity trade-offs are acknowledged but secondary here. Concept / Approach: ECL transistors are biased so they do not enter deep saturation. Avoiding saturation minimizes storage delay (the time to remove excess charge), which results in very low propagation delays and high speed. Step-by-Step Solution: Identify families and operating regimes. Recall that ECL uses differential pairs and does not saturate. Conclude ECL achieves higher speed than DTL/TTL/MOS in classic contexts. Verification / Alternative check: Data books list sub-nanosecond to a few-nanoseconds delays for ECL families, beating typical TTL and early MOS families under similar conditions. Why Other Options Are Wrong: DTL/TTL: slower due to transistor saturation and storage delays. MOS (early families): emphasized density and power, not peak speed at the time. None: invalid because ECL stands out for speed. Common Pitfalls: Confusing modern high-speed CMOS (very fast today) with historical “MOS” category in the options; the question targets classic families. Final Answer: ECL

Question 10

Truth table reasoning for multi-input logic: an AND gate has 7 inputs. Which single input pattern produces a logic-1 at the output?

Accepted Answer

Introduction / Context: AND gates output logic-1 only when all inputs are logic-1. With increasing inputs, the condition for a 1 output becomes more restrictive. This question reinforces the AND truth condition for a 7-input case. Given Data / Assumptions: Gate type: AND. Number of inputs: 7 (each input is 0 or 1). No inversion or additional logic is present. Concept / Approach: For an AND gate, output = 1 only if input_1 * input_2 * … * input_7 = 1. In binary logic, multiplication corresponds to logical AND; any 0 forces the product to 0. Step-by-Step Solution: List property: AND truth requires all inputs high. Check options: only the pattern with seven 1s satisfies the condition. Therefore select 1111111. Verification / Alternative check: Any pattern containing at least one 0 yields 0 at the output by AND logic definition. Why Other Options Are Wrong: Patterns with any 0 (e.g., 0000000, 0001111, 1110000) cannot produce 1 for an AND gate. “None” is invalid because there exists a valid pattern (all ones). Common Pitfalls: Confusing AND with OR; OR outputs 1 if any input is 1, but AND requires all be 1. Final Answer: 1111111

Question 11

Device technology identification: which of the following logic families is implemented with bipolar junction transistors (BJTs) as the primary switching devices?

Accepted Answer

Introduction / Context: Logic families are categorized by their underlying device technology. Bipolar and MOS technologies exhibit different speed, power, and density characteristics. Knowing which families are bipolar helps in understanding historical performance and interface levels. Given Data / Assumptions: Options include TTL, GaAs, NMOS, and CMOS. We identify the family fundamentally based on BJTs. No mixed-technology hybrids implied. Concept / Approach: Transistor–Transistor Logic (TTL) employs BJTs for both logic and amplification stages. By contrast, NMOS and CMOS use MOSFETs, while GaAs logic uses compound semiconductor FETs, not BJTs. Step-by-Step Solution: Recall technology: TTL → bipolar; NMOS/CMOS → MOSFET; GaAs → FETs in GaAs. Match option to the bipolar criterion: TTL. Verification / Alternative check: Data sheets and textbooks uniformly classify TTL as a bipolar family; its input/output levels and fan-out characteristics reflect BJT behavior. Why Other Options Are Wrong: GaAs: typically uses GaAs FETs, not BJTs. NMOS/CMOS: MOSFET-based, not bipolar. None: incorrect because TTL clearly fits. Common Pitfalls: Associating “high speed” with “bipolar” automatically; modern CMOS can be extremely fast, but the question is about device type, not speed. Final Answer: TTL

Question 12

Fundamentals of software: what do we call the ordered sequence of instructions that tells a computer how to process data and perform specific tasks?

Accepted Answer

Introduction / Context: At the heart of computing is the notion that a general-purpose machine executes a defined sequence of instructions. The artifact that organizes those instructions into a purposeful workflow is known as a program. Given Data / Assumptions: We distinguish between raw data and the instructions that operate on it. A single instruction is not the same as a complete, ordered set. Control signals originate from executing programs, not vice versa. Concept / Approach: A program is an executable specification: a list of instructions, structured with control flow (sequence, selection, iteration), that directs how input data are transformed into outputs. Data are passive, while a program is active and prescriptive. Step-by-Step Solution: Identify the object that encapsulates many instructions: program. Differentiate from one “instruction,” which is a single operation. Exclude “data,” which are values acted upon by the program. Verification / Alternative check: Definitions in introductory CS texts consistently define a program as a sequence or set of instructions executed by a computer. Why Other Options Are Wrong: Data: inputs/outputs, not procedural steps. Controls: generic term, not the formal artifact. Instruction: singular; the question asks for the ordered sequence. Common Pitfalls: Conflating configuration data with a program; configuration may guide behavior but is not executable instruction code by itself. Final Answer: program

Question 13

Base conversion practice: convert the binary number 1100011 (base 2) to hexadecimal (base 16). Choose the correct hex result.

Accepted Answer

Introduction / Context: Binary-to-hex conversion is efficient because 4 binary bits map directly to one hexadecimal digit. This is widely used in debugging, addressing, and compact representation of bit patterns. Given Data / Assumptions: Binary value: 1100011₂. No sign or fractional part. Left padding with zeros is allowed to complete 4-bit groups. Concept / Approach: Group the binary digits from right to left into 4-bit nibbles: 1100011 → 0110 0011. Convert each nibble to its hex digit. Step-by-Step Solution: Pad: 1100011 → 0110 0011. Convert: 0110₂ = 6₁₆; 0011₂ = 3₁₆. Combine: 63₁₆. Verification / Alternative check: Decimal cross-check: 1100011₂ = 97₁₀; 63₁₆ = 6*16 + 3 = 96 + 3 = 99? Wait, compute carefully: 6*16 = 96; 96 + 3 = 99. Re-evaluate binary: 1100011₂ = 64 + 32 + 2 + 1 = 99; matches 63₁₆. (Corrected: the decimal value is 99.) Why Other Options Are Wrong: 57₁₆ = 87₁₀; 46₁₆ = 70₁₀; 40₁₆ = 64₁₀. “None” is invalid because 63₁₆ is correct. Common Pitfalls: Forgetting to pad the leftmost group; miscomputing decimal equivalents when double-checking. Final Answer: 63₁₆

Question 14

Combinatorics of truth tables: an AND gate has 7 inputs. How many distinct input words (rows) appear in its complete truth table?

Accepted Answer

Introduction / Context: Truth tables enumerate all possible input combinations for a logic function. For n binary inputs, there are 2^n combinations. This question checks the ability to compute the size of the truth table for a 7-input logic gate (AND, but the count depends only on n). Given Data / Assumptions: Number of inputs n = 7. Each input is binary (0 or 1). Truth table includes all unique input combinations. Concept / Approach: The count of binary words of length n is 2^n. Thus, for n = 7, we have 2^7 total rows. This is independent of the logic function; AND, OR, XOR etc. share the same number of rows for the same n. Step-by-Step Solution: Use formula: total rows = 2^n. Compute: 2^7 = 128. Select 128 as the answer. Verification / Alternative check: List sizes grow as 2, 4, 8, 16, 32, 64, 128 for n = 1…7, confirming 128 for n = 7. Why Other Options Are Wrong: 64 = 2^6; 32 = 2^5; 16 = 2^4; these correspond to fewer inputs. “None” is incorrect because 128 is valid and present. Common Pitfalls: Using 2*n instead of 2^n; confusing number of outputs with number of table rows. Final Answer: 128

Question 15

Parity and XOR behavior: an XOR gate (extended to multiple inputs) asserts logic-1 for input words containing how many 1-bits?

Accepted Answer

Introduction / Context: XOR (exclusive-OR) is central to parity computations and error detection. When generalized to more than two inputs, XOR outputs 1 precisely when the count of 1-bits at its inputs is odd. Given Data / Assumptions: XOR is associative and commutative over binary inputs. Multiple-input XOR equals 1 if an odd number of inputs are 1. Even number of 1s yields 0. Concept / Approach: Define XOR truth for two inputs: 0⊕0=0, 0⊕1=1, 1⊕0=1, 1⊕1=0. Extending iteratively shows that XOR acts as a parity detector: it toggles with each encountered 1. Step-by-Step Solution: Consider a running XOR starting from 0. Each 1 flips the state; each 0 leaves it unchanged. Odd flips end at 1; even flips end at 0 → odd parity detection. Verification / Alternative check: Test examples: with three inputs 1,1,1 → 1⊕1⊕1 = 1; with four 1s → 1⊕1⊕1⊕1 = 0. Why Other Options Are Wrong: Even: XOR output is 0 for even count of 1s. “Different” is vague and does not precisely describe parity behavior. “All of the above” contradicts the unique parity rule. Common Pitfalls: Confusing XOR with OR; OR outputs 1 when any input is 1, regardless of parity. Final Answer: odd

Question 16

Parity testing with XOR networks: for an XOR-based parity checker, what outputs occur for even-parity input words versus odd-parity input words?

Accepted Answer

Introduction / Context: Parity checkers determine whether the number of 1-bits in a word is even or odd. XOR gates form the core of simple parity circuits because their output is 1 for odd parity and 0 for even parity. Given Data / Assumptions: Parity checker constructed from cascaded XORs. Definition: “even-parity word” → even count of 1s; “odd-parity word” → odd count of 1s. Output convention: logic-low = 0, logic-high = 1. Concept / Approach: Because XOR toggles its output for each input bit equal to 1, the final output equals 1 if the number of toggles is odd; equals 0 if even. Hence, even parity → 0, odd parity → 1. Step-by-Step Solution: Feed all bits of the word into a tree of XOR gates. Interpret the final XOR output: 0 indicates an even count of 1s; 1 indicates an odd count. Map to wording: even-parity word → low; odd-parity word → high. Verification / Alternative check: Test a 4-bit word with two 1s (even): XOR output 0. Test with three 1s (odd): XOR output 1. This matches the stated mapping. Why Other Options Are Wrong: “High, low” reverses the correct mapping. Options using “odd, even” or “even, odd” are not voltage levels and do not answer the electrical output behavior. “None” is invalid because a correct mapping exists. Common Pitfalls: Mixing up conventions when an additional inverter is used after XOR (some designs invert the output to signal “OK” on even parity). Here, pure XOR output is assumed. Final Answer: low, high

Question 17

Flip-flop transformation: if a single inverter is inserted such that one input of an SR latch receives D and the other receives the complement of D, what type of flip-flop results?

Accepted Answer

Introduction / Context: Flip-flops can be transformed by constraining their inputs. An SR latch/flip-flop with both inputs driven by complementary versions of the same signal behaves as a D (data) flip-flop, capturing the single input value. Given Data / Assumptions: Base device: SR latch/flip-flop. Inputs are forced to be complements: S = D and R = not D (via an inverter). Assume proper edge/level control to avoid illegal SR=1,1 state. Concept / Approach: With S = D and R = not D, only one of S or R can be asserted at a time. When D = 1, set is asserted and the device stores 1; when D = 0, reset is asserted and it stores 0. This exactly matches D flip-flop semantics: on the active control (clock or enable), Q_next = D. Step-by-Step Solution: Introduce an inverter so inputs are complementary. Map cases: D=1 → S=1,R=0 → Q set to 1; D=0 → S=0,R=1 → Q reset to 0. On each active transition/level, Q captures D → D-type behavior. Verification / Alternative check: Truth behavior of a D flip-flop is Q_next = D at the sampling event. The constrained SR realization reproduces this, confirming equivalence. Why Other Options Are Wrong: JK: requires independent J and K inputs, not forced complements of one signal. T: toggles when T=1; this construction does not toggle— it stores D. Master–slave JK: a specific clocked configuration of JK, not applicable here. Common Pitfalls: Driving S and R high simultaneously (forbidden); omitting proper gating/clocking when building edge-triggered D FF from level-sensitive latches. Final Answer: D flip-flop

Question 18

Digital circuit simplicity — quick visual guide: When informally comparing how simple or complex two logic circuit implementations are, a preliminary rule of thumb is to count the number of input _____ leads connected into the gates. What should fil…

Accepted Answer

Introduction / Context: Before performing a formal cost or timing analysis of a digital design, engineers often use quick heuristics to estimate implementation complexity. One such heuristic is to count how many individual input leads (wires) are feeding logic gates. This gives a fast sense of fan-in, interconnect density, and potential decoding complexity, which correlate with area, power, and sometimes delay. Given Data / Assumptions: The comparison is informal and preliminary (a quick guide, not a full synthesis report). We are evaluating input leads that physically connect signals into gate inputs. We are not counting the number of packages or buses as a whole, but the distinct wires entering logic inputs. Concept / Approach: Fan-in (the number of distinct input wires per gate) and the total count of input leads in a network directly affect logic effort and wiring complexity. More input wires generally imply more decoding stages or larger gates, which can mean higher input capacitance and potential increases in propagation delay or power. Step-by-Step Solution: Identify what is being counted: input leads that end on gate input pins.Relate this to complexity: more wires → more interconnect and often more logic.Conclude that the blank should be filled with “wire.” Verification / Alternative check: In schematic reviews, designers frequently tally input wires to estimate mux widths, decoder sizes, or PLA/PAL input load, which supports this heuristic. Why Other Options Are Wrong: “Bus” is a bundle, not an individual lead. “Gate” counts instances, not input leads. “All of the above” is incorrect because the rule focuses on input wires entering gates. Common Pitfalls: Confusing the number of signals on a bus with individual wires; a 16-bit bus equals 16 wires entering logic, not one. Final Answer: wire.

Question 19

Sequential logic fundamentals: In synchronous digital systems, clock signals are primarily used to _____ in different parts of the system.

Accepted Answer

Introduction / Context: Clock signals are the heartbeat of synchronous digital electronics. They define when sequential elements (like flip-flops and registers) sample inputs and update outputs. Understanding the purpose of the clock is essential for timing closure, reliable data transfer, and correct state-machine operation. Given Data / Assumptions: The system under discussion is synchronous (clocked). Clock edges coordinate the update of state elements. Clock lines are distinct from data and control signals. Concept / Approach: By distributing a periodic clock, designers ensure that all synchronous elements change state in a coordinated fashion on well-defined edges. This allows predictable timing, pipelining, and safe communication through registers. Clocks are not wall-clock timekeepers nor general serial data lines—although serial protocols may derive timing from dedicated clocks. Step-by-Step Solution: Identify the role of the clock: coordinate state updates.Link clock edges to setup/hold timing for flip-flops.Conclude that the clock synchronizes events across the system. Verification / Alternative check: Timing diagrams show signals sampled on rising/falling clock edges; STA (static timing analysis) assumes synchronous boundaries tied to the clock. Why Other Options Are Wrong: (a) and (b) relate to real-time measurement, not digital synchronization. (c) A clock does not carry the serial payload; it may accompany or embed timing for serial links, but the clock’s primary role is synchronization. Common Pitfalls: Confusing protocol clocks used for I/O with the system’s global synchronous clock; mixing data strobes with continuous clocks. Final Answer: to synchronize events in various parts of a system.

Question 20

IC component mix — what is rarely integrated? Which of the following electronic components is generally not found in ordinary monolithic integrated circuits?

Accepted Answer

Introduction / Context: Monolithic IC processes readily integrate transistors, diodes, and resistors. Inductors, however, are physically large and lossy on silicon, making them impractical for most “ordinary” digital and linear ICs. Recognizing which components are typically integrated helps in partitioning designs between on-chip and off-chip parts. Given Data / Assumptions: We consider standard silicon processes (CMOS, bipolar, BiCMOS) for mainstream ICs. Special RF or MEMS processes are excluded from “ordinary” ICs. We compare practical integrability, not theoretical possibility. Concept / Approach: Transistors are the core active elements; diodes are easily formed; resistors are implemented as diffused, polysilicon, or well resistors. Inductors require large areas and suffer from low Q when fabricated on-chip in general-purpose processes. Thus, most designs use external inductors when needed (e.g., switch-mode regulators, RF matching networks). Step-by-Step Solution: List commonly integrated elements: transistors, diodes, resistors.Assess practicality of on-chip inductors in ordinary processes: poor Q, high area.Select “inductors” as the component typically not found. Verification / Alternative check: Examine typical op-amp or logic IC internal schematics—no inductors are present; application circuits add external inductors if required. Why Other Options Are Wrong: Diodes, resistors, and transistors are fundamental and commonly integrated. Common Pitfalls: Assuming RF ICs with on-chip spirals are “ordinary”—those are specialized processes; in mainstream ICs, inductors remain external. Final Answer: inductors.

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