Q: Evaluate the power of two: what is the decimal value of 2^3 (two raised to the third power)?

Introduction / Context: Powers of two are the backbone of binary arithmetic, memory sizing, addressing, and timing divisions. Quickly converting between exponents and decimal values is a vital skill in digital design and computer engineering. Given Data / Assumptions: We are asked for 2^3. All arithmetic is in base-10 output for clarity. No units or scaling factors are present. Concept / Approach: Exponentiation with an integer exponent n means repeated multiplication by the base: a^n = a * a * ... * a (n times). For base 2, small exponents are frequently memorized: 2^0 = 1, 2^1 = 2, 2^2 = 4, and 2^3 = 8, continuing as 16, 32, 64, etc. Step-by-Step Solution: Compute 2^3 = 2 * 2 * 2.First multiplication: 2 * 2 = 4.Second multiplication: 4 * 2 = 8.Therefore, the decimal value of 2^3 is 8. Verification / Alternative check: Consider binary counting: after 1, 10, and 11, the fourth unique value is 100(2), which equals 4 in decimal; adding another doubling to reach 1000(2) confirms 2^3 = 8. Why Other Options Are Wrong: 2 and 4 correspond to 2^1 and 2^2, not 2^3. 6 is not a pure power of two; it is 2 * 3 not arising from exponentiation by an integer. Common Pitfalls: Mistaking multiplication count (e.g., doing only two multiplications for 2^3). Confusing doubling sequences with addition; exponentiation grows much faster than linear addition. Final Answer: 8

Q: Identify the statement that is NOT an advantage of digital technology and digital signal processing in electronic systems.

Introduction / Context: Digital electronics dominate modern systems because of robustness, programmability, and ease of storage and replication. Knowing why digital approaches are preferred helps engineers choose between analog and digital implementations for sensors, control, audio, and communications. Given Data / Assumptions: Digital signals take on discrete levels (typically two: LOW/HIGH). A comparison is being made to continuous-valued analog signals. We seek the statement that does not describe a digital advantage. Concept / Approach: Digital systems quantize information, which enables error detection/correction, noise immunity via thresholds, algorithmic programmability, and compact, reliable storage. By contrast, continuous-range variability is a property of analog systems and is not an inherent digital advantage. Step-by-Step Reasoning: Noise immunity: thresholding and regeneration make digital less susceptible to small disturbances.Programmability: software and firmware alter behavior without hardware redesign.Information storage: bits are easy to store, copy, and transmit with integrity checks.Continuous variation: this is characteristic of analog signals, not digital. Verification / Alternative check: Consider an A/D converter: it maps continuous analog values into discrete digital codes, illustrating that digital does not naturally vary continuously—it samples and quantizes instead. Why Other Options Are Wrong: Less affected by noise: genuine digital advantage due to logic thresholds and regeneration. Operation can be programmed: a hallmark advantage enabling rapid feature changes. Information storage is easy: bits in memory or on media are compact and durable with error correction. Common Pitfalls: Assuming digital is always superior; some high-fidelity or ultra-low-latency tasks still favor analog stages. Ignoring quantization and sampling errors introduced by digital conversion. Final Answer: The values may vary over a continuous range.

Q: Basic logic function: a decoder translates which type of information into which form in digital systems?

Introduction / Context: Decoders are core building blocks in digital systems. They interpret a compact binary code and assert exactly one of many outputs, enabling address selection, display driving, memory chip enables, and instruction decoding in CPUs. Given Data / Assumptions: Inputs are a coded (binary) set of lines, e.g., n bits. Outputs are noncoded, typically a 1-of-2^n set of lines. Active-HIGH or active-LOW conventions may be used, but the mapping is one-hot. Concept / Approach: Decoding expands compact coded information into explicit, mutually exclusive selections. For example, a 3-to-8 decoder uses 3 binary inputs to select 1 of 8 outputs. This “noncoded” set clearly identifies a single choice without further interpretation. Step-by-Step Solution: Consider inputs ABC (binary code).The decoder asserts only the output line corresponding to the binary value of ABC.Thus, coded information (ABC) becomes a noncoded, one-hot output vector. Verification / Alternative check: Seven-segment display drivers and memory address decoders are everyday examples; each input code turns on exactly one segment pattern or one memory bank enable line (with optional strobing or enable pins). Why Other Options Are Wrong: Noncoded to coded describes an encoder, the inverse device. “HIGHs to LOWs” or “LOWs to HIGHs” oversimplify logic level inversion and do not capture decoding’s mapping function. Common Pitfalls: Forgetting enable inputs; without proper enable the decoder may tri-state or force all outputs inactive. Not accounting for active-LOW outputs (bubble notation) when wiring external logic. Final Answer: coded information into noncoded form

Q: Integrated-circuit complexity classification: an IC containing roughly 100 to 10,000 equivalent logic gates per chip is categorized as:

Introduction / Context: Integrated circuits are traditionally grouped by their logic density. Knowing these categories helps interpret datasheets, historical literature, and system architecture discussions about scale and integration levels. Given Data / Assumptions: Gate-equivalent counts define categories. We compare SSI, MSI, LSI, and VLSI. Ranges are approximate and historically oriented. Concept / Approach: Common definitions: Small-Scale Integration (SSI) ≈ up to 10 gates, Medium-Scale (MSI) ≈ 10–100 gates, Large-Scale (LSI) ≈ 100–10,000 gates, and Very-Large-Scale (VLSI) > 10,000 gates. Modern SoCs far exceed VLSI, but the classical terms persist in education and cataloging. Step-by-Step Reasoning: Given the range 100 to 10,000 gates.Match with the standard taxonomy: this corresponds to LSI.Therefore, the correct classification is LSI. Verification / Alternative check: Typical MSI examples include 4-bit ALUs or counters; LSI historically covered early microcontrollers and larger memory arrays before the VLSI era expanded capacities dramatically. Why Other Options Are Wrong: SSI: too small—few gates only. MSI: generally 10–100 gates; below the specified range. VLSI: typically more than 10,000 gates; above the specified range. Common Pitfalls: Assuming exact boundaries; they are conventional, not hard limits. Confusing “gate count” with transistor count; different metrics can be quoted. Final Answer: LSI

Question 1

Basic definition – What is a digital-to-analog converter (DAC)? Choose the option that correctly describes the role of a DAC in everyday systems such as audio playback.

Accepted Answer

Introduction / Context: Digital systems represent information as numbers. To drive real-world devices such as speakers, motors, or displays, we often need an analog signal. A digital-to-analog converter (DAC) performs precisely this function. Given Data / Assumptions: Audio CDs, media players, and computers store audio as digital samples. Speakers require an analog voltage or current waveform. The question seeks a correct everyday description. Concept / Approach: A DAC accepts a digital code and outputs an analog level proportional to that code. In audio, rapid updates of the DAC reconstruct a time-varying waveform which is then filtered and amplified to drive speakers. The principle applies to many domains, including control systems and instrumentation. Step-by-Step Solution: Digital word → DAC input.DAC outputs an analog level corresponding to the code and reference.Reconstruction filter removes sampling images, yielding smooth audio.Amplifier drives the load with the recovered analog waveform. Verification / Alternative check: Block diagrams of CD/DVD/streaming players show: storage/decoder → digital filter → DAC → analog filter → amplifier → speaker. Why Other Options Are Wrong: Option B is misleading; DACs do not exist to “always” make things simpler. Option C describes storage, not conversion. Option D is a function of inverters or power electronics, not a DAC. Option E describes an ADC (the opposite direction). Common Pitfalls: Confusing sample rate with audio frequency content; reconstruction filtering is essential to avoid aliasing images in the output. Final Answer: It takes the digital information from an audio CD and converts it to a usable form.

Question 2

Exponent refresher: Evaluate the rule for exponents – any number raised to the power of 1 equals what?

Accepted Answer

Introduction / Context: Basic exponent rules are fundamental in electronics, controls, and signal processing. They underpin scientific notation, frequency scaling, and power calculations. Given Data / Assumptions: We consider real numbers a ≠ 0. The exponent is exactly 1. We apply the standard exponent identity laws. Concept / Approach: By definition of exponents and the identity element for multiplication, a^1 = a. This follows from the law a^m * a^n = a^(m+n). Setting m = 0 and n = 1 gives a^0 * a^1 = a^(0+1) = a^1. Since a^0 = 1, we have 1 * a^1 = a, so a^1 = a. Step-by-Step Solution: Start from a^m * a^n = a^(m+n).Let m = 0, n = 1: a^0 * a^1 = a^1.Because a^0 = 1, the left side reduces to 1 * a^1.Therefore, a^1 = a (the original number). Verification / Alternative check: Test with examples: 10^1 = 10; 2^1 = 2; (-3)^1 = -3. The identity holds universally for real numbers. Why Other Options Are Wrong: Zero (option A) would imply all numbers equal zero when exponent is 1, which is false. One (option B) corresponds to a^0, not a^1. Two (option C) is arbitrary and incorrect. Reciprocal (option E) corresponds to a^(-1), not a^1. Common Pitfalls: Mixing up a^0 = 1 and a^1 = a; keeping the exponent rules straight avoids algebra errors in engineering derivations. Final Answer: that number.

Question 3

Pulse timing computation: A periodic pulse train has a frequency of 2 kHz. Compute the pulse period T (time for one complete cycle).

Accepted Answer

Introduction / Context: Relating frequency and period is a fundamental skill in electronics and signal processing. Oscilloscopes, timers, and microcontroller peripherals all rely on the basic identity T = 1 / f. Given Data / Assumptions: Frequency f = 2 kHz. Assume a stable, periodic pulse train. We want the period T in seconds, then express in convenient units. Concept / Approach: The period is the reciprocal of frequency. For kilohertz, convert to hertz to avoid mistakes: 1 kHz = 1000 Hz. Keep unit consistency and then convert the result to milliseconds or microseconds as appropriate for readability. Step-by-Step Solution: Convert frequency: f = 2 kHz = 2000 Hz.Use the formula T = 1 / f.Compute: T = 1 / 2000 s = 0.0005 s.Express in microseconds: 0.0005 s = 500 µs. Verification / Alternative check: Sanity check: A higher frequency means a shorter period. Going from 1 kHz (T = 1 ms) to 2 kHz halves the period to 0.5 ms, i.e., 500 µs. Why Other Options Are Wrong: 5 ms (option A) corresponds to 200 Hz, not 2 kHz. 50 ms (option B) corresponds to 20 Hz. 2 µs (option D) would imply 500 kHz. 0.2 ms (option E) corresponds to 5 kHz. Common Pitfalls: Forgetting to convert kHz to Hz or mixing milliseconds with microseconds causes 10× or 1000× errors; always track units explicitly. Final Answer: 500 µs

Question 4

In digital electronics and pulse measurements, how is the rise time of a pulse formally defined—that is, the time it takes the waveform to transition between which two standardized amplitude points?

Accepted Answer

Introduction / Context: Rise time is a fundamental timing parameter for digital and pulse waveforms. Designers use it to characterize how quickly a signal edge transitions from a LOW level to a HIGH level. A precise, standardized definition avoids ambiguity across oscilloscopes, datasheets, and timing budgets for high-speed electronics and communication links. Given Data / Assumptions: A repetitive or single pulse that moves from a steady LOW to a steady HIGH. Amplitude is measured between the steady LOW and steady HIGH levels. Industry-standard thresholds are employed to minimize the effect of noise and saturation. Concept / Approach: Measuring from absolute 0% to 100% is overly sensitive to baseline noise and top-end compression. Therefore, the industry defines rise time as the interval required for the signal to move from 10% of the step amplitude to 90% of the step amplitude. These limits capture the main linear portion of the edge and yield consistent, comparable results. Step-by-Step Solution: Identify the LOW and HIGH steady-state levels of the waveform.Compute 10% level = LOW + 0.10 * (HIGH − LOW) and 90% level = LOW + 0.90 * (HIGH − LOW).On the oscilloscope, note the time when the rising edge crosses 10% and when it crosses 90%.Rise time = t(90%) − t(10%). Verification / Alternative check: Oscilloscopes typically offer automatic 10%–90% rise-time measurements. If the instrument uses 20%–80% by default, convert or reconfigure for consistency. For a well-behaved RC edge, the measured value will correlate with the circuit’s bandwidth limits (BW approximately 0.35 / rise time for a single-pole response). Why Other Options Are Wrong: Base line to maximum HIGH: too sensitive to noise and saturation regions. 10% to maximum HIGH: overshoots the accepted top threshold and inflates the result. Base line to 90%: includes noisy baseline and is nonstandard. Common Pitfalls: Measuring with inadequate oscilloscope bandwidth leads to artificially long rise times. Using probes without proper compensation distorts the observed edge. Confusing rise time with pulse width or propagation delay; they are different metrics. Final Answer: 10% of the pulse amplitude to 90% of the pulse amplitude

Question 5

Numeric conversion check: evaluate the expression 2^(-1) and give its decimal value.

Accepted Answer

Introduction / Context: Powers of two appear everywhere in digital systems, binary arithmetic, and signal processing. Being fluent with negative exponents is essential when interpreting fractional binary values, fixed-point formats, and resolution steps in analog-to-digital converters. Given Data / Assumptions: The expression is 2^(−1), which denotes a reciprocal power of two. We want the decimal (base-10) value. No additional scaling or units are involved. Concept / Approach: A negative exponent indicates a reciprocal: a^(−n) = 1 / (a^n). For base two, common values include 2^(−1) = 1/2, 2^(−2) = 1/4, and 2^(−3) = 1/8. These map directly to fractional steps in binary place values to the right of the binary point. Step-by-Step Solution: Start with the rule: 2^(−1) = 1 / 2^1.Compute 2^1 = 2.Therefore 2^(−1) = 1 / 2 = 0.5. Verification / Alternative check: Relate to binary fractions: the first fractional bit (2^(−1)) represents one-half. For example, the binary number 0.1(2) equals 0.5 in decimal, confirming the result. Why Other Options Are Wrong: 0.25 corresponds to 2^(−2). 0.1 is 1/10, not a reciprocal power of two. 0.05 equals 1/20; again, not a power-of-two fraction. Common Pitfalls: Confusing decimal fractions with binary place values (e.g., interpreting 0.1 as one-tenth regardless of base). Misreading the sign of the exponent; negative powers reduce magnitude. Final Answer: 0.5

Question 6

In digital logic level specifications, the voltage region between VL(max) (maximum recognized LOW) and VH(min) (minimum recognized HIGH) is considered:

Accepted Answer

Introduction / Context: Digital input thresholds specify safe voltage ranges that will be reliably interpreted as logic LOW or logic HIGH. Values that fall into the gap between those ranges create ambiguity, risking metastability or misinterpretation by logic gates and receivers. Given Data / Assumptions: VL(max): highest voltage guaranteed to be read as a logic LOW. VH(min): lowest voltage guaranteed to be read as a logic HIGH. Any voltage strictly between VL(max) and VH(min) does not meet either guarantee. Concept / Approach: The undefined region is intentionally reserved to provide noise margins. Designers should ensure signals transition quickly through this zone and avoid lingering, which can lead to oscillation, increased current draw, or incorrect logic levels, especially with slow edges or heavy capacitive loads. Step-by-Step Solution: Identify the specified logic thresholds from the device datasheet.Define valid LOW range: V ≤ VL(max); valid HIGH range: V ≥ VH(min).Recognize that the interval VL(max) < V < VH(min) is not guaranteed to be LOW or HIGH.Therefore this region is unacceptable for steady operation. Verification / Alternative check: Check datasheets (e.g., TTL, CMOS families). They explicitly label the middle zone as “indeterminate” or “no-man’s land,” reinforcing that logic must not remain there during normal operation. Why Other Options Are Wrong: Unknown: colloquial but not the accepted engineering term; the correct standard interpretation is that it is unacceptable for steady logic levels. Unnecessary: the region is necessary to provide noise margin, not superfluous. Between 2 V and 5 V: gives arbitrary numbers; actual thresholds depend on the specific logic family and supply voltage. Common Pitfalls: Driving inputs slowly through the zone; use Schmitt-trigger inputs or stronger drivers to avoid chatter. Ignoring ground bounce and supply noise that can push a borderline signal into the unacceptable region. Final Answer: unacceptable

Question 7

Evaluate the power of two: what is the decimal value of 2^3 (two raised to the third power)?

Accepted Answer

Introduction / Context: Powers of two are the backbone of binary arithmetic, memory sizing, addressing, and timing divisions. Quickly converting between exponents and decimal values is a vital skill in digital design and computer engineering. Given Data / Assumptions: We are asked for 2^3. All arithmetic is in base-10 output for clarity. No units or scaling factors are present. Concept / Approach: Exponentiation with an integer exponent n means repeated multiplication by the base: a^n = a * a * ... * a (n times). For base 2, small exponents are frequently memorized: 2^0 = 1, 2^1 = 2, 2^2 = 4, and 2^3 = 8, continuing as 16, 32, 64, etc. Step-by-Step Solution: Compute 2^3 = 2 * 2 * 2.First multiplication: 2 * 2 = 4.Second multiplication: 4 * 2 = 8.Therefore, the decimal value of 2^3 is 8. Verification / Alternative check: Consider binary counting: after 1, 10, and 11, the fourth unique value is 100(2), which equals 4 in decimal; adding another doubling to reach 1000(2) confirms 2^3 = 8. Why Other Options Are Wrong: 2 and 4 correspond to 2^1 and 2^2, not 2^3. 6 is not a pure power of two; it is 2 * 3 not arising from exponentiation by an integer. Common Pitfalls: Mistaking multiplication count (e.g., doing only two multiplications for 2^3). Confusing doubling sequences with addition; exponentiation grows much faster than linear addition. Final Answer: 8

Question 8

Identify the statement that is NOT an advantage of digital technology and digital signal processing in electronic systems.

Accepted Answer

Introduction / Context: Digital electronics dominate modern systems because of robustness, programmability, and ease of storage and replication. Knowing why digital approaches are preferred helps engineers choose between analog and digital implementations for sensors, control, audio, and communications. Given Data / Assumptions: Digital signals take on discrete levels (typically two: LOW/HIGH). A comparison is being made to continuous-valued analog signals. We seek the statement that does not describe a digital advantage. Concept / Approach: Digital systems quantize information, which enables error detection/correction, noise immunity via thresholds, algorithmic programmability, and compact, reliable storage. By contrast, continuous-range variability is a property of analog systems and is not an inherent digital advantage. Step-by-Step Reasoning: Noise immunity: thresholding and regeneration make digital less susceptible to small disturbances.Programmability: software and firmware alter behavior without hardware redesign.Information storage: bits are easy to store, copy, and transmit with integrity checks.Continuous variation: this is characteristic of analog signals, not digital. Verification / Alternative check: Consider an A/D converter: it maps continuous analog values into discrete digital codes, illustrating that digital does not naturally vary continuously—it samples and quantizes instead. Why Other Options Are Wrong: Less affected by noise: genuine digital advantage due to logic thresholds and regeneration. Operation can be programmed: a hallmark advantage enabling rapid feature changes. Information storage is easy: bits in memory or on media are compact and durable with error correction. Common Pitfalls: Assuming digital is always superior; some high-fidelity or ultra-low-latency tasks still favor analog stages. Ignoring quantization and sampling errors introduced by digital conversion. Final Answer: The values may vary over a continuous range.

Question 9

Basic logic function: a decoder translates which type of information into which form in digital systems?

Accepted Answer

Introduction / Context: Decoders are core building blocks in digital systems. They interpret a compact binary code and assert exactly one of many outputs, enabling address selection, display driving, memory chip enables, and instruction decoding in CPUs. Given Data / Assumptions: Inputs are a coded (binary) set of lines, e.g., n bits. Outputs are noncoded, typically a 1-of-2^n set of lines. Active-HIGH or active-LOW conventions may be used, but the mapping is one-hot. Concept / Approach: Decoding expands compact coded information into explicit, mutually exclusive selections. For example, a 3-to-8 decoder uses 3 binary inputs to select 1 of 8 outputs. This “noncoded” set clearly identifies a single choice without further interpretation. Step-by-Step Solution: Consider inputs ABC (binary code).The decoder asserts only the output line corresponding to the binary value of ABC.Thus, coded information (ABC) becomes a noncoded, one-hot output vector. Verification / Alternative check: Seven-segment display drivers and memory address decoders are everyday examples; each input code turns on exactly one segment pattern or one memory bank enable line (with optional strobing or enable pins). Why Other Options Are Wrong: Noncoded to coded describes an encoder, the inverse device. “HIGHs to LOWs” or “LOWs to HIGHs” oversimplify logic level inversion and do not capture decoding’s mapping function. Common Pitfalls: Forgetting enable inputs; without proper enable the decoder may tri-state or force all outputs inactive. Not accounting for active-LOW outputs (bubble notation) when wiring external logic. Final Answer: coded information into noncoded form

Question 10

Integrated-circuit complexity classification: an IC containing roughly 100 to 10,000 equivalent logic gates per chip is categorized as:

Accepted Answer

Introduction / Context: Integrated circuits are traditionally grouped by their logic density. Knowing these categories helps interpret datasheets, historical literature, and system architecture discussions about scale and integration levels. Given Data / Assumptions: Gate-equivalent counts define categories. We compare SSI, MSI, LSI, and VLSI. Ranges are approximate and historically oriented. Concept / Approach: Common definitions: Small-Scale Integration (SSI) ≈ up to 10 gates, Medium-Scale (MSI) ≈ 10–100 gates, Large-Scale (LSI) ≈ 100–10,000 gates, and Very-Large-Scale (VLSI) > 10,000 gates. Modern SoCs far exceed VLSI, but the classical terms persist in education and cataloging. Step-by-Step Reasoning: Given the range 100 to 10,000 gates.Match with the standard taxonomy: this corresponds to LSI.Therefore, the correct classification is LSI. Verification / Alternative check: Typical MSI examples include 4-bit ALUs or counters; LSI historically covered early microcontrollers and larger memory arrays before the VLSI era expanded capacities dramatically. Why Other Options Are Wrong: SSI: too small—few gates only. MSI: generally 10–100 gates; below the specified range. VLSI: typically more than 10,000 gates; above the specified range. Common Pitfalls: Assuming exact boundaries; they are conventional, not hard limits. Confusing “gate count” with transistor count; different metrics can be quoted. Final Answer: LSI

Question 11

Binary-to-decimal conversion: determine the decimal (base-10) value of the 5-bit binary number 10010.

Accepted Answer

Introduction / Context: Converting between binary and decimal is a foundational skill for interpreting addresses, register contents, and configuration fields in digital systems. Short binary words can be converted mentally by weighting each bit position by powers of two. Given Data / Assumptions: Binary number: 10010(2). Bit positions from LSB to MSB carry weights 2^0, 2^1, 2^2, 2^3, 2^4. We want the base-10 value. Concept / Approach: Each binary 1 contributes its positional weight; zeros contribute nothing. Sum all active weights to obtain the decimal value. Step-by-Step Solution: Write weights: from right to left: 2^0=1, 2^1=2, 2^2=4, 2^3=8, 2^4=16.Map bits: 1 0 0 1 0 corresponds to 2^4 + 2^1 = 16 + 2.Add contributions: 16 + 2 = 18.Therefore, 10010(2) = 18(10). Verification / Alternative check: Convert back: 18 / 2 gives remainders 0,1,0,0,1 (in reverse), yielding 10010(2), confirming the result. Why Other Options Are Wrong: 6 and 9 misplace bit weights. 20 adds an extra 2^2 or 2^0 weight that is not present. Common Pitfalls: Reading bit order right-to-left incorrectly. Forgetting that a zero bit contributes nothing regardless of position. Final Answer: 18₁₀

Question 12

Bit-width sizing: what is the minimum number of binary bits required to represent 748 distinct integer values (i.e., to uniquely encode the numbers 0 up to some maximum at least 748 − 1)?

Accepted Answer

Introduction / Context: Determining the required bit width for a counter, address space, or identifier is an everyday design decision. Using too few bits causes overflow; too many wastes resources. The key is relating the count of representable states to powers of two. Given Data / Assumptions: We must represent 748 different numbers (states). n bits represent 2^n distinct patterns. We seek the smallest n such that 2^n ≥ 748. Concept / Approach: Find successive powers of two until the count meets or exceeds the required number of states. This is equivalent to computing the ceiling of log2(748). Step-by-Step Solution: Compute nearby powers: 2^8 = 256, 2^9 = 512, 2^10 = 1024.Compare to requirement: 512 < 748 ≤ 1024.Therefore, 9 bits are insufficient, but 10 bits suffice.Minimum bit-width = 10 bits. Verification / Alternative check: Using logarithms: log2(748) ≈ ln(748)/ln(2) ≈ 6.619/0.693 ≈ 9.55. Taking the ceiling gives 10. This matches the power-of-two comparison method. Why Other Options Are Wrong: 7 or 8 bits yield at most 128 or 256 states, far below 748. 9 bits yield 512 states, still short of 748. Common Pitfalls: Off-by-one errors—confusing “numbers” with “maximum representable value.” For 748 distinct values, we require ≥748 states. Assuming decimal groups (e.g., thousands) map neatly to binary bit counts; always check powers of two. Final Answer: 10

Question 13

Convert the fractional binary number 10010.0100₂ to its decimal (base-10) equivalent.

Accepted Answer

Introduction / Context: Binary numbers with fractional parts occur in fixed-point arithmetic, digital signal processing, and fractional addressing. Converting such values to decimal requires understanding positional weights on both sides of the binary point. Given Data / Assumptions: Binary value: 10010.0100₂. Left of the binary point uses positive powers of two; right uses negative powers. No scaling or bias is applied beyond pure binary weighting. Concept / Approach: For a binary string a₄a₃a₂a₁a₀.b₁b₂b₃b₄, the decimal value is Σ aᵢ * 2^i + Σ bⱼ * 2^(−j). Only positions with bit 1 contribute to the sum. Step-by-Step Solution: Integer part 10010₂: weights are 2^4=16, 2^3=8, 2^2=4, 2^1=2, 2^0=1.Bits = 1 0 0 1 0 ⇒ contributions 16 + 2 = 18.Fractional part .0100₂: weights are 2^(−1)=0.5, 2^(−2)=0.25, 2^(−3)=0.125, 2^(−4)=0.0625.Bits = 0 1 0 0 ⇒ contribution 0.25 only.Total = 18 + 0.25 = 18.25. Verification / Alternative check: Convert the fractional portion by fraction: 0.0100₂ = 1/4 = 0.25. Add to the integer 18 to confirm 18.25. A calculator that accepts binary input or a spreadsheet using powers can reproduce the result exactly. Why Other Options Are Wrong: 24.50 and 16.25 use incorrect integer weights. 18.40 incorrectly treats 0.0100₂ as 0.40 decimal; binary fractions are not decimal tenths. Common Pitfalls: Confusing binary place values with decimal tenths and hundredths; in binary, the first fractional place is 1/2, then 1/4, 1/8, 1/16, etc. Reading the bit order from left to right without applying the correct weights for each position. Final Answer: 18.25

Question 14

Digital waveforms and duty cycle In a certain rectangular digital waveform, the total period T is equal to four times the pulse width t_on (that is, T = 4 * t_on). Based on this ratio, what is the duty cycle of the signal expressed as a percentage?

Accepted Answer

Introduction / Context: Duty cycle is a fundamental parameter for rectangular and pulse waveforms used in digital electronics, PWM motor control, switching power supplies, LED dimming, and timing systems. It tells us what fraction of one full period a signal remains in its active or HIGH state and is commonly expressed as a percentage. Given Data / Assumptions: Total period T equals four times the pulse width t_on (T = 4 * t_on). Duty cycle D% is defined with respect to the time the signal is HIGH during one complete period. The pulse is a clean rectangular waveform without additional substructure. Concept / Approach: By definition, duty cycle in percent is computed as (t_on / T) * 100. When period and on-time are related by a simple ratio, we substitute that ratio directly into the formula to get the percentage. This definition is widely used across oscilloscopes, function generators, and data sheets for digital circuits. Step-by-Step Solution: Write the duty cycle formula: D% = (t_on / T) * 100.Use the given relationship: T = 4 * t_on.Compute the ratio: t_on / T = t_on / (4 * t_on) = 1 / 4.Convert to percent: D% = (1 / 4) * 100 = 25%. Verification / Alternative check: Imagine one complete period split into four equal segments. If the signal is HIGH for only one segment and LOW for the remaining three, exactly one fourth of the time is HIGH, confirming a 25 percent duty cycle. Why Other Options Are Wrong: 0%: would require the signal never be HIGH, which contradicts having a nonzero t_on. 50%: would need t_on = T / 2, not T / 4. 100%: would mean always HIGH, impossible if T = 4 * t_on with finite LOW time. 75%: corresponds to t_on = 3 * T / 4, not given here. Common Pitfalls: Confusing pulse width with period or mixing milliseconds and microseconds. Always keep consistent units. Interpreting duty cycle as LOW time percentage instead of HIGH time percentage. Some systems define active time differently; read the context carefully. Final Answer: 25%

Question 15

Basic logic behavior of an OR gate For a standard OR gate in digital electronics, under what input condition is the output LOW?

Accepted Answer

Introduction / Context: OR gates are fundamental building blocks in digital logic. Understanding their truth tables is essential for analyzing combinational circuits, designing control logic, and debugging gate-level implementations in microcontrollers, FPGAs, and ASICs. Given Data / Assumptions: A standard positive-logic OR gate is used. Logic HIGH represents a logical 1, and logic LOW represents a logical 0. No degraded or undefined logic levels are considered; ideal digital behavior is assumed. Concept / Approach: An OR gate outputs HIGH if at least one of its inputs is HIGH. Conversely, its output is LOW only when every input is LOW. This behavior is captured succinctly by the Boolean expression: Y = A + B + C + ... where + denotes the OR operation. If every input equals 0, then Y = 0; otherwise Y = 1. Step-by-Step Solution: Start with the Boolean equation for an n-input OR: Y = A1 + A2 + ... + An.Evaluate the case when all inputs are 0: Y = 0 + 0 + ... + 0 = 0.For any case with at least one input 1, Y = 1, which is HIGH. Verification / Alternative check: Constructing a truth table confirms that the only row producing a LOW output is the row where all inputs are LOW. Any single HIGH immediately makes the output HIGH, reflecting the inclusive nature of OR. Why Other Options Are Wrong: Any input is LOW: an OR gate can still output HIGH if a different input is HIGH. Any input is HIGH: this actually makes the output HIGH, not LOW. All inputs are HIGH: also produces HIGH output. Alternating inputs: as long as at least one is HIGH, the output is HIGH. Common Pitfalls: Confusing OR with AND. AND requires all inputs HIGH for HIGH output; OR requires only one. Mixing active-low logic. With bubbles (inversion), truth behavior flips; here we assume standard positive logic. Final Answer: all inputs are LOW

Question 16

Serial data format in digital communication In serial format transmission, how are digital signals conveyed with respect to conductors and timing?

Accepted Answer

Introduction / Context: Digital systems exchange data either serially or in parallel. Serial links dominate modern interfaces (USB, PCIe, SATA) because they reduce pin count and simplify cabling while achieving very high data rates using advanced signaling and encoding methods. Given Data / Assumptions: We refer to the logical definition of serial format, not a specific physical layer. Clocking may be embedded or provided separately depending on protocol. Single-conductor phrasing implies one data path per direction (a reference or ground return is still required physically). Concept / Approach: In serial transmission, bits are sent one after another along the same data path, reusing the medium in time rather than space. This contrasts with parallel transmission, where multiple bits travel simultaneously across multiple conductors in lockstep with a shared clock or strobe. Step-by-Step Solution: Define serial: a sequence of bits transmitted over a single data channel.Recognize parallel: multiple data lines carry multiple bits at the same instant.Select the option that states single-conductor sequential transfer. Verification / Alternative check: Classic UART links (TX, RX) and SPI MOSI or MISO demonstrate serial behavior: each line conveys a time-ordered bit stream. Oscilloscope captures show a bit sequence, one bit at a time, on the line. Why Other Options Are Wrong: Many conductors simultaneously describes parallel format. Groups of eight signals suggests a byte-wide parallel bus, not serial. Binary coded decimal is a coding scheme, not a transmission geometry. Two wires per bit in parallel is a parallel definition, not serial. Common Pitfalls: Ignoring that physical links still need ground or differential pairs. Logically, serial uses one data path per direction. Assuming serial is always slow. Modern serial is extremely fast due to high signaling rates and encoding. Final Answer: sent over one conductor sequentially

Question 17

Digital storage elements Which type of logic device or circuit is primarily used to store multi-bit digital information for later use or transfer?

Accepted Answer

Introduction / Context: Temporary storage is essential in digital systems for pipelining, synchronization, and data movement between functional blocks. Storage elements may be arranged as single flip-flops or grouped into registers that can hold multi-bit words, often controlled by clocks and enables. Given Data / Assumptions: A register is an array of flip-flops capable of storing multiple bits. We are comparing basic logic components by primary function. No specific register type (parallel-load, shift register) is implied; general storage is intended. Concept / Approach: Registers are built from flip-flops to store N-bit values. They support loading, holding, and sometimes shifting, making them the standard choice for CPU registers, pipeline stages, and interface boundary registers. Counters do store state but their main purpose is counting sequences, not general data storage. Step-by-Step Reasoning: Identify device whose primary role is storage of multi-bit data → register.Distinguish counters: optimized for advancing through states in response to clock pulses.Inverters and buffers process signals but do not store data. Verification / Alternative check: Any microarchitecture diagram shows multiple registers for data, addresses, and intermediate values. Datasheets for parts like 74HC273 (octal D-type flip-flop) label them as registers, highlighting their storage function. Why Other Options Are Wrong: Counter: primarily counts; storage is incidental to sequencing. Inverter: logical negation, no memory. Buffer: drive strength or isolation, no memory. Decoder: translates codes, not storage. Common Pitfalls: Assuming any sequential device is a register. Only devices designed to hold arbitrary data words are considered registers. Confusing shift registers with counters; shift registers do store but for serial movement, still registers by function. Final Answer: Register

Question 18

Understanding GAL devices in programmable logic Which statement correctly describes a Generic Array Logic (GAL) device in terms of programmability and technology?

Accepted Answer

Introduction / Context: Generic Array Logic devices were introduced to improve upon PALs by enabling reprogrammability. GALs became staples in digital design for glue logic, address decoding, and small state machines, particularly before CPLDs and FPGAs became ubiquitous. Given Data / Assumptions: GAL devices use nonvolatile memory cells (often EEPROM) for configuration. They are implemented using CMOS technology for low power and high integration. We consider standard commercial GALs from major vendors. Concept / Approach: Unlike earlier one-time programmable PALs that required windowed UV erasure or were blown fuses, GALs can be erased and reprogrammed electrically many times. Their CMOS implementation brings lower standby power and better noise margins compared with older bipolar families. Step-by-Step Reasoning: Identify programmability: GALs are reprogrammable via EEPROM cells.Identify technology: mainstream GALs are CMOS-based devices.Combine both traits → reprogrammable and a CMOS device. Verification / Alternative check: Look at datasheets for GAL16V8 or GAL22V10 devices. They explicitly mention CMOS technology and electrically erasable programmability, enabling many design cycles with a single chip during prototyping. Why Other Options Are Wrong: One-time programmable: describes many PALs, not GALs. Reprogrammable only: incomplete, ignores CMOS implementation. CMOS only: incomplete, ignores reprogrammability feature. Bipolar and not reprogrammable: incorrect for GALs. Common Pitfalls: Confusing GALs with PALs or PEEL devices. Always check the erasure and technology notes. Assuming GALs are functionally identical to CPLDs; GALs are simpler and smaller scale. Final Answer: reprogrammable and a CMOS device

Question 19

Multiplexer fundamentals A multiplexer (MUX) performs which input/output role in digital systems?

Accepted Answer

Introduction / Context: Multiplexers are selection devices used to route one of many input signals to a single output line under the control of select inputs. They are essential in data routing, resource sharing, and implementing logic functions by selection rather than explicit gates. Given Data / Assumptions: Standard MUX behavior is assumed (e.g., 2-to-1, 4-to-1, 8-to-1, 16-to-1). Control lines select exactly one input at a time. Transmission is ideal; ignore analog details and tristate behavior unless specified. Concept / Approach: A MUX funnels multiple candidate inputs into a single pathway. The Boolean function implemented equals the sum of selected minterms based on select lines, which is why MUXes can synthesize logic functions with appropriate input wiring. Step-by-Step Reasoning: Identify role: choose exactly one source among many.Confirm I/O structure: several inputs → one output.Select lines determine which input reaches the output. Verification / Alternative check: Reference typical parts like 74HC157 (quad 2-to-1) or 74HC151 (8-to-1). Their truth tables show one output reflecting one selected input at a time based on select pins and enable control. Why Other Options Are Wrong: One input to many outputs describes a demultiplexer, not a multiplexer. One input and one output is just a buffer. Several inputs and several outputs could be a crossbar or bus switch, not a simple MUX. Several outputs selected to one input inverts the concept. Common Pitfalls: Confusing MUX with DEMUX; they are mirrors of each other. Forgetting enable pins that can tristate or disable the output. Final Answer: several inputs and one output

Question 20

Parallel data format in digital interfaces What does parallel format mean regarding how digital signals are carried on conductors?

Accepted Answer

Introduction / Context: Parallel interfaces such as legacy printer ports and wide memory buses transfer multiple bits simultaneously. Understanding what makes a format parallel helps explain bandwidth, pin count, skew issues, and why many systems have moved to high-speed serial links for longer distances. Given Data / Assumptions: A parallel bus carries multi-bit groups simultaneously. Each bit line is a separate conductor (plus ground and control lines). Clocking method is not specified; some parallel systems have a separate clock or strobe. Concept / Approach: Parallel transmission achieves higher instantaneous throughput by spatially distributing bits across multiple lines. The cost is more wiring, larger connectors, and the need to manage timing skew and crosstalk across those lines. Step-by-Step Reasoning: Define parallel: N-bit word placed on N conductors at the same time.Identify conductor mapping: one conductor per bit signal.Note that control and clock lines may be additional conductors. Verification / Alternative check: Look at a typical 8-bit data bus: D0 through D7 are separate pins in the connector or package. Oscilloscope captures show multiple lines changing together on clock edges or strobes. Why Other Options Are Wrong: Several signals on each conductor is the opposite of parallel; that is multiplexing. Binary vs hexadecimal is a coding view, not a wiring format. No clock needed is not inherent; many parallel buses still use a clock or strobe. One-wire time-division multiplexing describes serial or TDM, not parallel. Common Pitfalls: Forgetting return paths and grounds. Real buses need proper reference conductors. Ignoring skew limits; longer parallel cables often need careful timing control. Final Answer: each digital signal has its own conductor

Digital Concepts Questions