Question 1

Since microprocessor CPUs cannot execute human-readable mnemonics directly, into what form must these assembly mnemonics be translated before execution?

Accepted Answer

Introduction / Context: Processors read and execute sequences of bits, not textual mnemonics. Assemblers and toolchains therefore convert symbolic instructions into the exact binary encodings defined by the instruction set architecture (ISA). Given Data / Assumptions: Assembler input: MOV A,B or similar mnemonics. CPU input requirement: binary op-codes and operands. Hexadecimal is a human-friendly representation of binary, not a separate executable form. Concept / Approach: The ISA specifies bit fields for operation, addressing mode, and operands. The assembler encodes these into binary. Hex is often used as a compact notation for binary but the hardware ultimately consumes binary voltage levels. Step-by-Step Solution: Write assembly source with mnemonics.Run assembler → produce object code (binary) and optionally hex listings.Loader places binary into memory for execution.CPU fetches and interprets binary op-codes. Verification / Alternative check: Disassemblers convert binary back to mnemonics; this reversibility demonstrates the binary-to-text mapping. Why Other Options Are Wrong: A: Hex is just a numbering system for displaying binary; the CPU still operates on binary. C: Assembly language is the mnemonic source, not the executable form. D: Not all choices are correct; only binary is fundamental to execution. Common Pitfalls: Confusing “hex file” formats (e.g., Intel HEX) with the actual in-memory binary bytes; hex files are transport representations. Final Answer: binary machine code

Question 2

Clarify terminology: what is the essential difference between mnemonic code (assembly language) and machine code in microprocessor programming?

Accepted Answer

Introduction / Context: Understanding the distinction between human-readable assembly and processor-readable machine code is foundational for embedded and systems programming. Assemblers bridge these two representations. Given Data / Assumptions: Mnemonic code uses alphabetic tokens (e.g., MOV, ADD, JMP). Machine code consists of binary patterns (often shown in hex). Both encode the same operations but in different forms for different audiences (humans vs. hardware). Concept / Approach: Machine code is the literal bit pattern that the CPU decodes and executes. Mnemonics are symbolic names for these operations, improving readability and maintainability. Labels and directives further assist organization in mnemonic form. Step-by-Step Solution: Consider instruction MOV A,B (mnemonic, readable).Assembler maps it to a specific binary op-code (e.g., a byte value).CPU fetches and executes the binary instruction from memory.Therefore, the difference lies in representation: text vs. bits. Verification / Alternative check: Use an assembler and a disassembler: one direction turns mnemonics into binary; the other reverses the process, confirming equivalence of meaning but difference of form. Why Other Options Are Wrong: A: Incorrect; they are different representations. C: Reverses the correct mapping. Common Pitfalls: Believing that hex listings are different from machine code; they are just a readable numeral system for binary bytes. Final Answer: Machine codes are in binary, mnemonic codes are in shorthand English.

Question 3

In a microprocessor-based system, which bus primarily carries the control signals that direct peripherals and memory to perform specific operations (read, write, acknowledge, interrupt, etc.)?

Accepted Answer

Introduction / Context: System buses partition the roles of communication between the CPU, memory, and peripherals. Differentiating the data, address, and control buses is a core concept in digital system design and troubleshooting. Given Data / Assumptions: Address bus: selects which memory or I/O location is targeted. Data bus: carries the actual data values being read or written. Control bus: carries signals defining the operation and timing. Concept / Approach: To perform any transaction, the CPU places an address on the address bus, the operation type on the control bus (e.g., RD, WR), and transfers data on the data bus. Additional control lines can include clock, reset, interrupt requests, and acknowledge signals. Step-by-Step Solution: Identify the bus that encodes operation intent → control bus.Recognize that data values traverse the data bus, not control.Understand that the address bus selects targets, not operations.Therefore, the bus that directs ICs about the operation is the control bus. Verification / Alternative check: Examine timing diagrams of a memory read cycle: signals like RD, WR, ALE, and IO/M are asserted on control lines to define the transaction. Why Other Options Are Wrong: Data bus: carries payload, not directives. Address bus: carries location indices, not read/write control. Address decoder bus: not a standard bus name; decoding happens on address lines using logic. Common Pitfalls: Assuming any single bus controls everything; in reality, the three-bus model separates roles for clarity and performance. Final Answer: control bus

Question 4

Microprocessor buses — standard widths In classic microprocessor architecture fundamentals, how many bits are commonly used on the data bus to transfer data between the CPU, memory, and I/O devices?

Accepted Answer

Introduction / Context: The data bus is the set of parallel conductors that carries actual data values between the central processing unit, memory, and input/output peripherals. Understanding its typical width helps learners connect processor families (8-bit, 16-bit, 32-bit) to performance and design trade-offs. Given Data / Assumptions: The question refers to foundational microprocessor systems commonly taught at the introductory level. Many classic CPUs and peripheral chips exchange data over an 8-bit data bus. Higher-width buses do exist (16, 32, 64), but are not the default in entry-level discussions. Concept / Approach: Historically, mainstream introductory microprocessors (and their memory/I-O ecosystems) used 8-bit data buses. An 8-bit bus moves one byte per transfer, which aligns with byte-addressable memory and keeps board complexity low for teaching and simpler embedded designs. Step-by-Step Solution: Identify “typical/commonly used” width in early and educational systems → 8 bits.Relate to byte-sized data transfers → 1 transfer = 1 byte.Confirm alternatives → 7 and 9 bits are nonstandard; 16 bits belong to wider, costlier designs. Verification / Alternative check: Survey of classic microcontrollers and early CPUs (e.g., foundational teaching platforms) shows widespread use of 8-bit data buses, with memory chips and peripherals designed around byte-wide interfaces. Why Other Options Are Wrong: 7 or 9: uncommon widths for general data buses. 16: valid for 16-bit families, but not the most common foundational width. Common Pitfalls: Equating address-bus width with data-bus width; these are independent. Also assuming “wider is always better,” ignoring cost and complexity. Final Answer: 8

Question 5

Control bus sharing — true or false? In a typical microprocessor system, do the control bus and memory devices share a single bidirectional bus line in the same way as the data bus?

Accepted Answer

Introduction / Context: A microprocessor system uses three conceptual buses: address, data, and control. While the data bus is bidirectional, the control bus carries timing and control signals with fixed directions (from CPU to devices or vice versa). Clarifying this prevents wiring and design misunderstandings. Given Data / Assumptions: “Typical” microprocessor system organization is assumed. Control bus includes dedicated signals such as read, write, memory/IO select, interrupt lines, and acknowledge lines. Data bus is bidirectional; address bus is usually unidirectional from CPU to memory/I-O. Concept / Approach: The term “bus” implies shared conductors, but not every signal shares a single bidirectional line. Control signals are distinct lines with defined directions; they are not a single bidirectional conductor shared like the data bus. Therefore the statement that control bus and memories “share a bidirectional bus” is inaccurate. Step-by-Step Solution: Identify bus roles → address (uni), data (bi), control (mixed fixed-direction lines).Check claim → “control bus and memories share a bidirectional bus” → incorrect generalization.Conclude → The statement is false. Verification / Alternative check: Block diagrams in textbooks show separate labeled control lines rather than a single bidirectional “control/data” line shared with memory. Why Other Options Are Wrong: “True” would imply control behaves like data lines, which is not the case. Common Pitfalls: Assuming that because signals share a connector or backplane they are bidirectional; directionality is defined per signal. Final Answer: False

Question 6

A microprocessor with the necessary support circuits will include at least two memory ICs: ROM or EPROM, and a RAM.

Accepted Answer

True

Question 7

LDA addr and STA addr are Fortran language instructions stored in an external memory IC for a microprocessor.

Accepted Answer

False

Question 8

Conversion from assembly language to machine language can be done by the programmer through a process called hand assembly.

Accepted Answer

True

Question 9

I/O-mapped systems identify their input and output devices by giving them an 8-bit port number.

Accepted Answer

True

Question 10

The software used to drive a microprocessor-based system is called FORTRAN.

Accepted Answer

False

Question 11

The stack is a data storage area in RAM used by certain microprocessor operations.

Accepted Answer

True

Question 12

A microcontroller integrates multichip systems with RAM, ROM, and I/O.

Accepted Answer

True

Question 13

Programs written for the 8080A must have slight modifications to run on the 8085A.

Accepted Answer

False

Question 14

The 8085 software is compatible with the 8080A.

Accepted Answer

True

Question 15

Assembly language is written using mnemonics: MVI, DCR, JZ.

Accepted Answer

True

Microprocessor Fundamentals Questions