Microprocessors and Microcontrollers Unit II

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Questions and Answers

What is the maximum amount of memory that the 8086 can access?

512 KB

2 MB

4 MB

1 MB (correct)

Which of the following is not a feature of the 8086 microprocessor?

Supports 64K I/O ports

Operates with a 33% duty cycle clock

Uses a 40-pin dual in-line package

Includes 32-bit registers (correct)

What are the two blocks that make up the architecture of the 8086?

Control Unit and Arithmetic Logic Unit

Data Unit and Memory Unit

Execute Unit and Bus Interface Unit (correct)

Core Unit and Management Unit

What is the primary function of the Bus Interface Unit (BIU) in the 8086?

Perform all external bus operations Signup and view all the answers

How does the 8086 achieve instruction execution efficiency?

Through the combination of BIU and EU Signup and view all the answers

Which component of the 8086 is responsible for maintaining the instruction queue?

Bus Interface Unit Signup and view all the answers

What voltage supply is required for the operation of the 8086 microprocessor?

+5V Signup and view all the answers

How many bytes of instruction can the 8086 pre-fetch from memory at one time?

6 bytes Signup and view all the answers

What does the status signal S5 indicate?

Status of the Interrupt Enable Flag (IF) bit Signup and view all the answers

What is the function of the BHE signal during data transfers?

To indicate transfer of data over higher order data bus Signup and view all the answers

How does the RESET signal affect the operation of the processor?

It causes the processor to stop current activity and start from FFFF0H Signup and view all the answers

What does a logic 1 on the M/IO signal indicate?

A memory operation is taking place Signup and view all the answers

Which signal is used to indicate whether data needs to be transmitted or received?

DT/R Signup and view all the answers

When does the Address Latch Enable (ALE) become logic 1?

When a valid address is present on the bus Signup and view all the answers

What occurs when the TEST input goes low?

Execution continues Signup and view all the answers

Which of the following best describes the behavior of status signals S4 and S3?

They show which segment register is in use Signup and view all the answers

What does the 8086 microprocessor do during period T3 of a memory read cycle?

It provides valid data and maintains it until the read operation terminates. Signup and view all the answers

What does the WR signal indicate during T2 of a memory write cycle?

A write operation is about to follow. Signup and view all the answers

Which signals are activated at T1 to initiate a write cycle in the 8086?

M/IO and DT/R Signup and view all the answers

When does the 8086 switch RD to inactive logic level during a read cycle?

Late during T4. Signup and view all the answers

What role does DEN play during the memory operation of the 8086?

It enables the external circuitry for data transfer. Signup and view all the answers

What occurs during the T1 time state of the 8086 bus cycle?

The 20-bit address is output on the multiplexed address/data bus. Signup and view all the answers

What signal indicates a read cycle is in progress during T2?

RD Signup and view all the answers

Which signal remains active throughout the four periods of the bus cycle?

M/IO Signup and view all the answers

How is the address latched in external circuitry during T1?

By the high level of the ALE pulse. Signup and view all the answers

What is a group of states in the 8086 bus cycle referred to as?

Machine Cycle Signup and view all the answers

Which of the following statements about the status bits during T2 is true?

S3 to S6 are output on the upper four address bus lines. Signup and view all the answers

What action takes place in case the reader input is not activated before T3?

A wait state is inserted between T3 and T4. Signup and view all the answers

During which time states does the status bit S0 to S2 remain active?

T1 and T2 Signup and view all the answers

What is the purpose of the Count Register in the 8086 architecture?

Serves as a counter in loop and string manipulation instructions. Signup and view all the answers

In the context of the Data Register, what role does the DH register play?

It holds the high-order word in a multiplication operation. Signup and view all the answers

What is the primary function of the Instruction Pointer (IP) register?

Indicates the address of the next instruction to be executed. Signup and view all the answers

Which of the following correctly describes the Stack Pointer (SP) register?

It points to the program stack. Signup and view all the answers

Which registers are involved in indexed addressing for data in the stack segment?

SP and BP. Signup and view all the answers

How many bits are utilized in the Flag Register of the 8086 architecture for condition flags?

Six bits. Signup and view all the answers

What does the Source Index (SI) register primarily facilitate?

Serves as a source data address in string manipulation. Signup and view all the answers

What is the combined function of the CL and CH registers?

Create a 16-bit Count Register named CX. Signup and view all the answers

Study Notes

Introduction to 8086 Microprocessors

8086 is a 16-bit microprocessor with a 20-bit address bus, allowing access to 1 MB of memory (2^20 memory locations).
Supports up to 64K I/O ports and provides 14 registers, each 16-bits in size.
Utilizes a multiplexed address and data bus (AD0-AD15 and A16-A19).
Operates with a +5V power supply in a 40-pin dual in-line package.

Architecture of 8086 Processors

Comprises two main units: Bus Interface Unit (BIU) and Execution Unit (EU).
BIU handles all bus operations, instruction fetching, operand reading/writing, and address calculations.
EU executes instructions from the instruction queue, enabling pipelining for enhanced efficiency.

Register Organization of 8086

The count register (CX) consists of two 8-bit registers (CL and CH), used for loop and string manipulation.
Data register (DX) comprises two 8-bit registers (DL and DH), utilized for I/O operations and arithmetic calculations.
Contains general-purpose registers: Stack Pointer (SP), Base Pointer (BP), Source Index (SI), Destination Index (DI), and Instruction Pointer (IP).

Memory Segmentation of 8086

8086 employs memory segmentation for efficient memory management.
Segment registers assist in the organization of memory for code, data, and stack segments.
Memory addressing combines the contents of segment registers and the instruction pointer.

Pin Diagram of 8086

The pin configuration supports a variety of functions, including addressing and data transfer.
Key signals: ALE (Address Latch Enable), M/IO (memory/I/O operation), DT/R (data transmit/receive), and RESET for processor initialization.

Timing Diagrams for 8086

Bus cycles involve specific time states (T1-T4) crucial for memory read/write operations.
A memory read cycle outputs a 20-bit address in T1 and enables data transfer in T3.
A memory write cycle follows a similar sequence, with data being transmitted during T2 and maintained until T4.

Interrupts of 8086

8086 supports interrupts for managing processor priorities and event handling.
Interrupt Enable Flag (IF) is used to control interrupt handling status.

Control Signals and Timing States

Control signals like ALE indicate valid address presence, while M/IO signals if the operation is memory or I/O related.
Data direction is signaled by DT/R, where logic 1 indicates data transmission.

Summary of Operations

Instruction cycle timing is determined by specific machine cycles which vary based on the operation (memory read, memory write, etc.).
The combined architecture of BIU and EU allows for simultaneous instruction fetch and execution, optimizing performance through pipelining.

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Description

This quiz covers Unit II of the Microprocessors and Microcontrollers course, focusing on the 8086 microprocessor. It includes topics such as its architecture, register organization, memory segmentation, and interrupts, providing a comprehensive overview of the 8086's functionalities.