Question 1

Intel 8085A architecture — how many buses are part of the microprocessor? In the 8085A microprocessor system, count the distinct buses that connect and organize data flow (consider address, data, and control classifications).

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Introduction / Context: Classic microprocessors such as the Intel 8085A organize external communication via buses. Differentiating the address, data, and control buses clarifies how the CPU selects devices, transfers data, and orchestrates timing. This fundamental partitioning appears across many 8-bit families and remains relevant in microcontroller bus matrices today. Given Data / Assumptions: 8085A exposes an address bus, data bus, and a set of control/status lines. Some pins are multiplexed (AD0–AD7) but logically belong to the address/data buses at different times. We count logical buses, not pin counts. Concept / Approach: The 8085A uses a 16-bit address bus (A8–A15 plus multiplexed AD0–AD7), an 8-bit data bus (AD0–AD7 during data phase), and control/status lines (RD, WR, IO/M, ALE, READY, etc.) that form the control bus. Thus there are three buses: address, data, and control. Multiplexing does not reduce the count of logical buses; it only saves pins by time-sharing functions. Step-by-Step Solution: Identify logical roles → address selects device/location.Data bus carries operand/instruction bytes.Control bus carries read/write strobes and status signals.Total distinct buses → 3. Verification / Alternative check: Any 8085A block diagram shows three labeled bus groups. The ALE signal demultiplexes AD lines to separate address and data externally. Why Other Options Are Wrong: 2 buses: ignores the control bus. 5 or 8 buses: overcounts; sub-groups are not separate buses at the architectural level. 4 buses: no standard fourth bus exists in the basic 8085A memory/IO interface. Common Pitfalls: Confusing physical multiplexing with the logical bus count. Final Answer: 3

Question 2

Bus contention prevention — which block ensures only one IC drives the bus at a time? In a shared-bus microprocessor system, what logic block guarantees that only the selected device is enabled, preventing two ICs from simultaneously writing differe…

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Introduction / Context: Bus conflicts occur when more than one device drives a shared bus line concurrently, potentially causing excessive current and corrupted data. Proper chip-select (CS) logic ensures that, for any address, at most one device has its outputs enabled. Understanding the role of the address decoder is fundamental to robust memory and I/O mapping. Given Data / Assumptions: Multiple memory and I/O devices share an 8- or 16-bit data bus. Each device has an enable/chip-select input. The system uses non-overlapping address ranges for each device. Concept / Approach: An address decoder interprets high-order address lines (and sometimes control lines like IO/M) to produce one-hot chip-select signals. Only the addressed device's CS is asserted, so only that device's output drivers are enabled. All others remain in high-impedance, eliminating contention. The control bus provides strobes (RD/WR), but without correct decoding, multiple devices could respond simultaneously. Step-by-Step Solution: Partition address space into unique windows for each device.Design decoder (e.g., 3-to-8 or PLD) to assert exactly one CS for any valid address range.Gate the device's tri-state outputs with CS and RD/WR to drive the bus only when selected.Result: only one active driver at a time; no bus conflict. Verification / Alternative check: Memory maps and schematics show decoders (e.g., 74HC138, PAL/GAL) generating CS lines; logic truth tables demonstrate mutual exclusivity. Why Other Options Are Wrong: Control bus: carries strobes but does not select a single device by address. Control instructions: software constructs; hardware-level contention prevention is via decoding. CPU: issues addresses but does not inherently provide device-specific CS signals. Tri-state buffer without CS: offers high-Z capability, but without decoding it could still be enabled simultaneously. Common Pitfalls: Overlapping decode ranges that cause multiple CS signals to assert; always verify decode equations. Final Answer: address decoder

Question 3

I/O-mapped addressing — how are devices identified? In classic Intel-style I/O-mapped systems (separate I/O space), input/output devices are identified and selected by assigning each device a specific ________.

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Introduction / Context: Some CPU architectures, such as the 8085 and 8086 families, distinguish between memory space and I/O space. In an I/O-mapped (isolated I/O) scheme, IN and OUT instructions access ports addressed separately from memory. Understanding how devices are identified in this space is key to designing I/O maps and decoders. Given Data / Assumptions: Intel 8085 uses 8-bit port addressing with IN/OUT instructions. Memory-mapped I/O (alternative scheme) uses memory addresses instead. We focus on the isolated I/O case. Concept / Approach: With I/O-mapped I/O on the 8085, each device is selected by an 8-bit port number (0–255). The CPU places this number on the lower address/data bus during I/O cycles, and IO/M along with RD/WR strobes indicate an I/O operation. The decoder then asserts the chip-select for the device assigned to that port, ensuring only the intended peripheral responds. Step-by-Step Solution: Choose unique 8-bit port numbers for devices (e.g., keyboard at 0x10, display at 0x20).CPU executes IN/OUT with the port number; bus shows the port on AD lines.I/O decoder asserts the matching chip-select; device drives or latches the data bus.Result: device identification via 8-bit port number. Verification / Alternative check: Assembly examples show “IN 20H” or “OUT 10H” addressing ports directly, consistent with 8-bit I/O addressing on the 8085. The 8086 extends capability via DX for 16-bit ports, but the 8085 remains 8-bit. Why Other Options Are Wrong: 16-bit port number: not for the 8085 (that is more associated with 8086/88 using DX). 8-bit buffer number and 8-bit instruction: not addressing schemes for isolated I/O. 7-bit device ID (I2C): different serial bus protocol, unrelated to 8085 I/O-mapped ports. Common Pitfalls: Mixing isolated I/O with memory-mapped I/O; decoding differs substantially. Final Answer: 8-bit port number

Question 4

Digital I/O architecture (output port) In a typical microprocessor or microcontroller system, which hardware circuit is placed at the interface of an output port so that written data is held stable and presented to the external device until the next…

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Introduction / Context: An output port is the hardware point where a processor's internal data bus hands data off to the outside world (LEDs, relays, DACs, and so on). The circuit used must capture the value during a write cycle and hold it stable long after the bus has moved on to other operations. Given Data / Assumptions: The CPU provides brief write strobes (WR) and address selects (chip select) to target a port. External devices often need a steady logic level, not a momentary pulse on the system bus. The output port must remember (store) the last data until a new write occurs. Concept / Approach: A transparent latch or an edge-triggered register captures data from the data bus when the write strobe and the address decoder indicate an addressed write. After the brief write, the bus releases the data lines, but the latch continues to drive the external pins with the stored value. This separation of capture and hold action is the essence of an output port. Step-by-Step Solution: Use address decoding to generate a chip-select pulse for the chosen output port.Combine chip-select with WR to produce a load enable for the latch.On the active load, the latch stores D7..D0 (or the bus width).Between writes, the latch holds the output stable so the field device sees a continuous logic level. Verification / Alternative check: Observe with a logic analyzer: bus data exists only for the write window, yet the port pin stays at the written level afterwards—proof that storage (latching) is occurring. Why Other Options Are Wrong: Decoder: Selects the device; it does not store data. Tristate buffer: Controls bus direction/connection; it doesn't remember values. None of the above: Incorrect because a latch is the standard solution. Common Pitfalls: Confusing input and output port hardware: inputs typically use tristate buffers to place data onto the bus only when selected, while outputs require storage to maintain levels. Final Answer: latch

Question 5

Basic computer terminology In a computer system, what do we call the physical components you can touch and see (for example, chassis, boards, chips, cables, keyboard, and monitor)?

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Introduction / Context: Clear terminology helps separate what a system is made of from what it does. Computer engineering distinguishes between tangible parts and the instructions that run on them. This question tests recognition of those fundamental terms. Given Data / Assumptions: Physical items include printed circuit boards, ICs, displays, keyboards, storage drives, and interconnects. Non-physical items include programs, operating systems, and microcode. Some items sit in between—such as firmware (software stored in nonvolatile memory inside hardware). Concept / Approach: Use standard definitions: Hardware is the collection of physical, tangible components. Software is the set of programs and data that direct hardware. Firmware is software tightly bound to the hardware (for example, code in ROM/Flash on a device), often serving as low-level control. Step-by-Step Solution: Identify that the prompt asks specifically for items you can physically touch.Map this to the definition of hardware: the physical apparatus.Exclude software (intangible programs) and firmware (software stored in hardware memory).Select the option that matches the tangible set: hardware. Verification / Alternative check: Introductory computing texts list hardware examples (CPU, RAM modules, power supply) versus software examples (apps, OS). Only the former are tactile. Why Other Options Are Wrong: Software: Not physical; cannot be touched. Firmware: Software residing in hardware; still not a physical object itself. None of the above: Incorrect because “hardware” is exactly correct. Common Pitfalls: Thinking firmware is hardware because it is stored on a chip. The chip is hardware; the code within is firmware (software). Final Answer: hardware

Question 6

Computer system interfaces The devices and subsystems that allow a computer to communicate with users and with other computers are collectively known as:

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Introduction / Context: Modern systems interact with people and other devices through a variety of interfaces: keyboards, displays, network adapters, USB, serial ports, and more. The umbrella term for these pathways is input/output, abbreviated I/O. Given Data / Assumptions: I/O encompasses both input (to the computer) and output (from the computer). CPU (central processing unit) and ALU (arithmetic logic unit) are internal processing blocks, not communication peripherals. Interfaces may be built-in or provided via expansion hardware. Concept / Approach: Classify components by function: the CPU executes instructions; the ALU performs arithmetic and logic; I/O handles data exchange at the system boundary. Anything that senses the world (input) or affects the world (output) falls under I/O. Step-by-Step Solution: Identify the question's focus: communication with users/other computers.Map communication hardware to the I/O category.Exclude CPU and ALU, which process data but do not directly handle external interaction.Choose “I/O.” Verification / Alternative check: Block diagrams in textbooks show I/O subsystems on the periphery of the CPU/memory complex, interfacing through buses and controllers. Why Other Options Are Wrong: CPU: Executes instructions; not the set of peripherals used for communication. ALU: Only a sub-block of the CPU doing arithmetic/logic. None of the above: Incorrect since “I/O” is standard terminology. Common Pitfalls: Confusing interfaces (I/O) with the protocols (USB, Ethernet). Protocols run over I/O hardware. Final Answer: I/O

Question 7

System buses and directionality Among the standard processor buses, which one carries information in both directions and therefore is bidirectional under normal operation?

Accepted Answer

Introduction / Context: Classic microprocessor architectures expose three fundamental buses: address, data, and control. Understanding which ones are unidirectional versus bidirectional is essential for board design and timing analysis. Given Data / Assumptions: The CPU initiates memory or I/O cycles by placing an address on the address bus. Data can flow from CPU to memory/I/O (writes) and from memory/I/O to CPU (reads). Control signals indicate the type and phase of the transfer (for example, RD̄, WR̄). Concept / Approach: Address lines are driven by the CPU to select a location—there is no need for memory to drive an address back, so the address bus is unidirectional (CPU → memory/I/O). The data bus must support both read and write directions, so it is bidirectional and often implemented with tristate or turn-around cycles. Step-by-Step Solution: Identify the address bus as a selector (unidirectional out of CPU).Recognize that data must flow in both directions depending on read/write.Thus, the data bus is bidirectional.Choose “data bus.” Verification / Alternative check: Examine timing diagrams: during reads, memory drives the data bus; during writes, the CPU drives. This confirms bidirectionality. Why Other Options Are Wrong: Address bus: Typically one-way from CPU. Both buses: Not correct because only the data bus is bidirectional in standard designs. None of the above: Incorrect; the data bus fits. Common Pitfalls: Some SoCs use shared multiplexed address/data buses in legacy designs, but the directional concept remains: data lines change direction; address does not. Final Answer: data bus

Question 8

CPU registers and results Which processor register keeps track of the current result of arithmetic or logic operations so that new results can be stored and used immediately by subsequent instructions?

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Introduction / Context: Classic CPU architectures revolve around a small set of special-purpose registers with distinct roles. The accumulator is historically the workhorse register for arithmetic/logic, especially in accumulator-based instruction sets (for example, 8051, 8085). Given Data / Assumptions: Many instructions implicitly use a specific register for ALU operations. Subsequent instructions often read the most recent result without extra moves. Other special registers serve flow control and stack management. Concept / Approach: The accumulator is the primary destination/source for arithmetic and logic operations. While modern RISC machines are general-register architectures, the conceptual role remains: a register holds the latest ALU result for immediate reuse. The program counter/instruction pointer track addresses, not data results; the stack pointer tracks the top of the stack. Step-by-Step Solution: Identify the register associated with ALU results.Exclude control-flow registers (PC/IP) and stack management (SP).Select “accumulator.”Relate to instruction examples: ADD operand → result lands in accumulator. Verification / Alternative check: Examine instruction sets (for example, 8085: ADD r adds register r to accumulator A; result in A). Documentation confirms its result-holding role. Why Other Options Are Wrong: Stack pointer: Tracks stack top address. Program/instruction pointer: Hold the next instruction address, not results. Common Pitfalls: Assuming every architecture uses an explicit accumulator; some use general registers, but the question context matches accumulator-based designs. Final Answer: accumulator

Question 9

Microprocessor history According to common textbook timelines, in which year was the first widely adopted 8-bit microprocessor introduced to the market (for example, the Intel 8080 era)?

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Introduction / Context: The evolution from 4-bit to 8-bit microprocessors marked a major leap for early personal computing and embedded systems. Recognizing the timeline helps contextualize software tools, instruction sets, and system buses of the period. Given Data / Assumptions: “First widely adopted 8-bit microprocessor” commonly refers to the Intel 8080 generation used in many early microcomputer kits. The question aligns with conventional academic timelines rather than an exhaustive historical list. Other 8-bit devices existed around the same era, but 8080 catalyzed broader adoption. Concept / Approach: Associate key processor releases with their years. The Intel 8080 was introduced in 1974 and rapidly became the CPU of choice for early hobbyist and commercial systems, paving the way for Zilog Z80 and MOS 6502 later in the decade. Earlier, Intel 8008 (1972) was also 8-bit, but 8080 is typically cited in introductory courses as the landmark for “first mainstream 8-bit.” Step-by-Step Solution: List candidate years.Recall 8080 release year as 1974.Select 1974 as the commonly taught answer.Note that other options do not match this milestone. Verification / Alternative check: Historical summaries of early micros: 4004 (1971, 4-bit), 8008 (1972, 8-bit), 8080 (1974, 8-bit, widely adopted), 8085 (1976), 8086 (1978). Why Other Options Are Wrong: 1969: Pre-microprocessor era. 1979/1985: Later generations (for example, 8088-based PCs and beyond). Common Pitfalls: Confusing earliest 8-bit (8008 in 1972) with the commonly cited “first widely adopted 8-bit,” which many curricula attribute to 8080 in 1974. Final Answer: 1974

Question 10

I/O addressing models What is the technique called in which each I/O device is assigned one or more addresses within the memory address space, allowing reads/writes to I/O to use the same instructions used for memory?

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Introduction / Context: Processors interact with peripherals using either a separate I/O space (isolated I/O) or by placing device registers into the regular memory map (memory-mapped I/O). Understanding the naming clarifies how software accesses devices. Given Data / Assumptions: The CPU can perform loads/stores to addresses. Peripherals expose control/status/data registers as addressable locations. Using the same instruction set for memory and I/O simplifies compilers and code. Concept / Approach: Memory-mapped I/O assigns devices to unique addresses in the system memory map. Software uses standard load/store instructions to interact, and the bus fabric routes those transactions to the appropriate device instead of RAM. This contrasts with isolated/ported I/O (for example, x86 IN/OUT instructions) that uses a distinct I/O space. Step-by-Step Solution: Recognize that the question describes device registers residing in the memory address space.Recall the standard term: memory-mapped I/O.Select the corresponding option.Note advantages: uniform instruction set, easy pointer arithmetic; disadvantages: possible cache coherency considerations. Verification / Alternative check: Most microcontrollers (ARM Cortex-M, RISC-V MCUs) use memory-mapped I/O for peripheral registers documented in datasheets. Why Other Options Are Wrong: Ported I/O/dedicated/wired I/O: Nonstandard or ambiguous labels for the described technique. Common Pitfalls: Forgetting to mark device regions as noncacheable; treating I/O like RAM can cause stale reads unless memory attributes are set correctly. Final Answer: memory-mapped I/O

Question 11

Terminology check What do we collectively call all computer programs and associated data used by a machine, including the operating system, applications, and utilities?

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Introduction / Context: Clear distinctions between software, firmware, and hardware are foundational in IT and electronics. The term “software” encompasses everything from the operating system to user applications and scripts. Given Data / Assumptions: Programs are sequences of instructions executed by the CPU. Data includes configuration, resources, and files used by those programs. These items exist as information, not physical components. Concept / Approach: Software is the general term for programs and their data. Firmware is software stored in nonvolatile memory on hardware devices (for example, router firmware). Hardware is the physical infrastructure that executes the software. Step-by-Step Solution: Identify that the question asks for “all computer programs.”Recall the broad term: software.Exclude firmware (a subset) and hardware (physical components).Select “software.” Verification / Alternative check: Intro to Computing references define software as OS + applications + utilities + data files associated with them. Why Other Options Are Wrong: Firmware: A special class of software embedded in hardware; not all programs. Hardware: Physical parts, not programs. None of the above: Incorrect because “software” is standard. Common Pitfalls: Calling firmware “hardware” because it resides on a chip; the storage medium is hardware, the content is software. Final Answer: software

Question 12

Digital I/O architecture (input port) In a typical microprocessor system, which circuit is used at the interface of an input port so that external device data can be conditionally placed onto the CPU data bus only when the port is selected?

Accepted Answer

Introduction / Context: Unlike output ports, which must store and continuously drive a value, input ports must share the CPU data bus with many other devices. The hardware must therefore connect the external input to the bus only at the right time to avoid contention. Given Data / Assumptions: Many devices share the data bus. Only the addressed input port should drive the bus during a read. Control signals include RD̄ and chip-select generated by address decoding. Concept / Approach: A tristate buffer presents three states: logic 0, logic 1, and high-impedance (Hi-Z). When not selected, the buffer is disabled and its output is Hi-Z—electrically disconnected from the bus. When selected during a read, the buffer enables and drives the bus with the device's data, preventing bus fights. Step-by-Step Solution: Use an address decoder to produce a chip-select for the input port.Combine chip-select with RD̄ to enable the tristate buffer only on valid reads.External device's data appears on the CPU data bus while enabled.When the read ends, return to Hi-Z to allow other devices to use the bus. Verification / Alternative check: Logic analyzer traces show only one device driving the bus during a read; bus lines float or are pulled when the port is not selected, proving effective tristate control. Why Other Options Are Wrong: Decoder: Selects the device but does not isolate it from the bus. Latch: Stores data, appropriate for outputs; does not provide Hi-Z isolation by itself. None of the above: Incorrect because tristate buffer is standard practice. Common Pitfalls: Leaving multiple input sources enabled simultaneously causes bus contention. Always gate the buffer with address select and RD̄. Final Answer: tristate buffer

Question 13

8085A datapath components Within the Intel 8085A microprocessor, which named block performs arithmetic and logic functions such as addition, subtraction, AND, OR, XOR, increment, and compare?

Accepted Answer

Introduction / Context: Microprocessor block diagrams separate control, datapath, and interface functions. The arithmetic logic unit (ALU) is the core datapath block that executes arithmetic and bitwise operations on register data. Given Data / Assumptions: Target device: Intel 8085A, a classic 8-bit microprocessor. Operations include arithmetic (add, subtract) and logic (AND, OR, XOR, NOT). Control and status flags reflect ALU results (zero, sign, carry, parity, auxiliary carry). Concept / Approach: The ALU receives operands from internal registers (for example, accumulator and a general-purpose register), performs the selected operation, sets flags, and writes the result back to a destination register. The CPU (central processing unit) is the overall chip; ALU is a specific functional sub-block within it. I/O refers to external interface logic, not the executing arithmetic engine. Step-by-Step Solution: Identify the block responsible for arithmetic/logic inside the CPU.Name that block: the arithmetic logic unit (ALU).Distinguish from the broader CPU and from I/O subsystems.Select “ALU.” Verification / Alternative check: 8085A documentation lists ALU operations and related flags; instruction mnemonics (ADD, SUB, ANA, ORA, XRA, CMP) all target the ALU. Why Other Options Are Wrong: CPU: The entire processor; too broad. I/O: Handles external data transfers; not arithmetic. None of the above: Incorrect because ALU is the established term. Common Pitfalls: Using “CPU” and “ALU” interchangeably. The CPU contains the ALU but also includes registers, control unit, buses, and timing circuits. Final Answer: ALU

Question 14

In Intel 8085A microprocessor architecture, which register keeps track of the memory address of the next instruction (next op-code) to be fetched and executed by the CPU? Provide the most appropriate register name used for instruction sequencing in …

Accepted Answer

Introduction / Context: The instruction execution cycle of an 8-bit microprocessor such as the Intel 8085A depends on a special register that points to the address of the next op-code. Understanding which register performs this role is fundamental to microprocessor programming, debugging, and system design. Given Data / Assumptions: Target device: Intel 8085A (8-bit CPU). We are asked which register holds the address of the next instruction. Typical internal registers include the accumulator, general-purpose registers, the stack pointer, and the program counter. Concept / Approach: The CPU fetches the next instruction from memory at an address held in a dedicated sequencing register. After fetching, the CPU normally increments this register so that it points to the subsequent instruction, unless a branch, jump, call, or interrupt modifies the control flow. Step-by-Step Solution: Identify the register that stores the next instruction address → program counter (PC).Recognize that stack pointer (SP) instead tracks the top of the stack, not the instruction stream.Note that the accumulator stores arithmetic/logic results, not addresses.In some architectures an instruction pointer exists, but in 8085A the standard term is program counter. Verification / Alternative check: Observe any program that uses a jump or call: the destination address is loaded into the program counter, immediately changing the next fetch location, confirming the PC's role. Why Other Options Are Wrong: Stack pointer: references stack memory, not instruction addresses. Instruction pointer: not the conventional 8085A term; PC is used. Accumulator: an 8-bit data register for ALU operations, not addressing. Common Pitfalls: Confusing PC with SP when analyzing subroutine calls and returns; remember calls push the current PC to the stack, and returns pop it back. Final Answer: program counter

Question 15

In microprocessor status architecture, what do we call the single-bit indicators that are set or cleared to reflect the results of arithmetic or logical operations (e.g., zero, carry, sign)?

Accepted Answer

Introduction / Context: Every classic microprocessor, including the Intel 8085A, maintains one-bit indicators reflecting the outcome of ALU operations. These indicators enable conditional branching and efficient program control based on computation outcomes. Given Data / Assumptions: The question asks for the standard term used for one-bit status indicators. Typical indicators include zero, carry, sign, parity, and auxiliary carry. These bits are grouped in a dedicated status or flag register. Concept / Approach: After each arithmetic/logic operation, the ALU updates one or more status bits. Instructions such as JZ (jump if zero) or JC (jump if carry) read these bits to decide the next control flow. Step-by-Step Solution: Identify the specific one-bit indicators → status flags.Recognize their home register → flag register or PSW (program status word) in some architectures.Understand how conditional instructions test these bits to branch.Conclude that the correct term is “flags.” Verification / Alternative check: Trace an addition such as 0xFF + 0x01: the carry flag sets; a compare that finds equality sets the zero flag. Observing branching behavior confirms the role of flags. Why Other Options Are Wrong: Registers: too general; flags are bits within a specific register. Monitors/Decisions: not standard processor vocabulary for status bits. Common Pitfalls: Assuming flags are manual inputs; in reality, the ALU hardware sets/clears them automatically unless explicitly manipulated by instructions. Final Answer: flags

Question 16

Microprocessor unit composition: identify the three foundational sections of a classic microprocessor unit (MPU) responsible for sequencing, storage, and computation.

Accepted Answer

Introduction / Context: A microprocessor unit (MPU) integrates circuitry to control instruction flow, store working data, and perform arithmetic/logic operations. Recognizing these foundational blocks helps in understanding instruction cycles and hardware-software interaction. Given Data / Assumptions: The focus is on internal MPU sections, not external memory or I/O devices. Standard blocks: control/timing, registers, and ALU. These blocks cooperate during fetch, decode, execute, and write-back phases. Concept / Approach: The control and timing section generates control signals and orchestrates the instruction cycle. The register section provides fast local storage (accumulator, general registers, PC, SP). The ALU executes arithmetic and logic operations using register operands. Step-by-Step Solution: List internal MPU blocks → control & timing, registers, ALU.Eliminate options including memory and I/O (external to the MPU proper).Confirm that operands are not a structural block; they are data items stored in registers/memory.Select the combination that matches the canonical MPU structure. Verification / Alternative check: Any block diagram of 8085/8086 identifies these sections within the CPU chip. Why Other Options Are Wrong: C/D include memory or I/O which are system-level, not strictly MPU-internal sections. A mentions “operand” which is a data concept, not a hardware section. Common Pitfalls: Confusing “CPU” with the broader “computer system.” The question targets the CPU's internal organization. Final Answer: control and timing, register, and arithmetic/logic unit (ALU)

Question 17

In embedded systems, the software permanently stored in non-volatile memory to drive microprocessor-based hardware (initialization, control, device handling) is commonly referred to as:

Accepted Answer

Introduction / Context: Embedded systems rely on dedicated software stored in ROM, Flash, or OTP that initializes hardware, controls peripherals, and provides the device's core behavior. This persistent software sits between pure hardware and higher-level applications. Given Data / Assumptions: The term sought is for non-volatile, device-specific software. It is used to bootstrap and control microprocessor or microcontroller hardware. It may be written in assembly or C but is stored as machine code. Concept / Approach: Firmware is distinct from application software (which may be upgradable or stored externally) and from hardware configuration. It provides the essential operational logic so that a device can start, self-test, and function as intended. Step-by-Step Solution: Identify the storage and role → program in ROM/Flash that runs on startup.Note examples: BIOS/UEFI, router firmware, printer firmware.Select the umbrella term used industry-wide → firmware.Differentiate from language names (assembly, BASIC), which are merely ways to author the code. Verification / Alternative check: Device updates are called “firmware updates,” reinforcing the standard terminology. Why Other Options Are Wrong: Assembly language/BASIC: programming languages, not the persistent product itself. Machine language code: describes the encoding, not the role (many programs are machine code but not all are firmware). Common Pitfalls: Equating “firmware” strictly with assembly; modern firmware is often C/C++ compiled to machine code but remains firmware due to its role and residence in non-volatile memory. Final Answer: firmware

Question 18

Assembler tools: which type of computer program translates mnemonic assembly instructions into executable machine code for a target microprocessor?

Accepted Answer

Introduction / Context: Microprocessors execute binary op-codes. Humans prefer readable mnemonics (e.g., MOV, ADD, JMP). The bridge between these worlds is a translation tool that maps symbolic instructions and labels into machine code and addresses. Given Data / Assumptions: Input: assembly source with mnemonics and directives. Output: object code or executable with resolved op-codes and addresses. Target: specific instruction set (e.g., 8085A, 8086). Concept / Approach: An assembler performs lexical analysis, parsing, symbol resolution (labels), and code generation. It may also produce listing files, symbol tables, and relocation records for linkers. Step-by-Step Solution: Provide assembly as input to the assembler.Assembler converts mnemonics to binary op-codes and computes addresses.Linker/loader may combine modules and place code in memory.Processor executes the resulting machine code. Verification / Alternative check: Compile an example (e.g., MVI A,00H). The listing shows hex bytes corresponding to the mnemonic, confirming the translation step. Why Other Options Are Wrong: Debug: diagnostic tool, not a translator. C++/Fortran: high-level languages; their compilers output machine code but not from assembly mnemonics. Common Pitfalls: Confusing assemblers and compilers. Compilers translate high-level constructs; assemblers map one-to-one mnemonics to op-codes. Final Answer: assembler

Question 19

Instruction-encoding terminology: when referring to instruction words, what does the term mnemonic represent in assembly programming for microprocessors such as the 8085A?

Accepted Answer

Introduction / Context: Assembly languages use human-readable tokens to represent operations and addressing modes. These tokens are designed to be memorable and concise, simplifying low-level programming and documentation. Given Data / Assumptions: An instruction typically includes an operation and optional operands. Examples: MOV A,B (move), ADD M (add memory), JMP 2000H (jump). We must identify what “mnemonic” denotes within such instructions. Concept / Approach: The mnemonic is the symbolic name of the operation (op-code) such as MOV, ADD, SUB, JMP. Operands specify sources, destinations, or addresses. Assemblers translate mnemonics into numeric op-codes understood by the CPU. Step-by-Step Solution: Break an instruction into parts: operation + operands.Recognize the operation's symbolic name → mnemonic.Operands may be registers, immediates, or memory addresses.Conclude that a mnemonic abbreviates the operation, not the data or address. Verification / Alternative check: Assembler reference manuals list mnemonics mapped to op-code bytes, confirming the role of mnemonics. Why Other Options Are Wrong: A/C: describe operands, not the operation keyword. D: machine language is binary/hex; mnemonics are symbolic, not machine code. Common Pitfalls: Assuming mnemonics imply exact op-code encoding across architectures; the same mnemonic may assemble to different op-codes on different CPUs. Final Answer: a short abbreviation for the operation to be performed

Question 20

Identify the data width and interface style of the Intel 8085A: what kind of CPU is the 8085A in terms of word size and data transfer (serial vs. parallel)?

Accepted Answer

Introduction / Context: Classifying a microprocessor by word size and data movement style helps predict performance, instruction set density, and peripheral interfacing. The Intel 8085A is a classic starter CPU in many curricula and labs. Given Data / Assumptions: 8085A is historically known as an 8-bit microprocessor. It communicates with memory and peripherals using parallel buses. Address bus and data bus widths are standard features in its datasheet. Concept / Approach: An 8-bit CPU processes 8-bit data in the ALU in a single cycle, with larger values handled across multiple cycles. A parallel interface transfers multiple bits simultaneously across data/address lines, enabling higher throughput compared to serial transfer. Step-by-Step Solution: Identify ALU width → 8 bits for 8085A.Identify bus organization → 8-bit data bus (multiplexed AD0–AD7), 16-bit address capability via demultiplexing.Confirm transfers occur in parallel on the bus lines.Therefore, the 8085A is an 8-bit parallel CPU. Verification / Alternative check: Typical kits show address/data bus lines on 8085 trainers; timing diagrams indicate parallel bus transactions. Why Other Options Are Wrong: 16-bit parallel: describes CPUs like 8086 (internally 16-bit). 8-bit serial: contradicts 8085A's parallel bus architecture. None of the above: incorrect because option C is accurate. Common Pitfalls: Confusing “address bus width” (16-bit) with “data width” (8-bit). The CPU is still categorized as 8-bit. Final Answer: 8-bit parallel CPU

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