Computer I/O Synchronization Quiz

Questions and Answers

What does an initial value of FGI = 0 signify?

The output device is busy.

The INPR register is ready but empty. (correct)

Data has been received in the INPR register.

The OUTR register is ready for data.

Which of the following is a characteristic of program-controlled I/O?

It is the most hardware-intensive I/O method.

It requires continuous CPU attention. (correct)

It allows for simultaneous CPU and I/O operation.

It reduces CPU involvement in data transfer.

What action does the CPU take upon detecting an interrupt request?

Switches to an idle state.

Stops the current task and processes the interrupt. (correct)

Immediately continues the current task.

Ignores the request until the next cycle.

What is the function of the IEN (Interrupt-enable flip-flop R)?

It controls whether interrupts can be acknowledged or not. Signup and view all the answers

In program-controlled input, what does the command 'SKI (device number)' do?

Skips the next instruction if data is present. Signup and view all the answers

What is a drawback of program-controlled I/O?

It can slow down the CPU to I/O speeds. Signup and view all the answers

How does the interrupt mechanism improve CPU efficiency?

By allowing I/O devices to signal when they are ready, reducing idle CPU time. Signup and view all the answers

What is signified by the instruction 'LOP, SKO (device number)' in output operations?

The output process must wait until the device is ready. Signup and view all the answers

What is the first step in executing a Memory Reference instruction?

Place effective address in AR. Signup and view all the answers

In the execution of the ISZ (Increment and Skip-if-Zero) instruction, what happens if the result after incrementing is zero?

The PC is incremented by 1. Signup and view all the answers

How is the Input Register (INPR) in an input-output configuration used?

To receive serial information from the keyboard. Signup and view all the answers

Which timing signal initiates the execution of a Memory Reference instruction?

T4 Signup and view all the answers

What does the acronym AC stand for in the context of the CPU and memory operations?

Accumulator Signup and view all the answers

In the memory instruction 'STA', what does the execution primarily involve?

Store the accumulator's data into the memory. Signup and view all the answers

What does the Output Register (OUTR) store information for?

Storing output for the printer. Signup and view all the answers

During which timing signal is the Memory Reference instruction 'AND to AC' executed?

D0T5 Signup and view all the answers

What function does the Input Flag (FGI) serve in the input-output configuration?

Signals the presence of new input data. Signup and view all the answers

Which Memory Reference instruction involves transferring the program counter value before the execution phase?

BSA Signup and view all the answers

What is the primary function of memory reference instructions in the basic computer?

To facilitate the transfer of data between memory and registers Signup and view all the answers

Which part of the basic computer is primarily responsible for handling input-output configurations?

Control unit Signup and view all the answers

How is program-controlled data transfer typically achieved in the design of the basic computer?

Through sequential instruction execution that manipulates data in registers Signup and view all the answers

What is the role of interrupts in the basic computer's operations?

To signal the CPU to stop its current operations and address an event or condition Signup and view all the answers

Which of the following components primarily impacts CPU performance with I/O operations?

The speed of memory access Signup and view all the answers

In what way does the address register contribute to memory reference instructions?

It tracks the location in memory for fetching operands. Signup and view all the answers

What is the significance of the effective address (EA) in instruction execution?

It is the direct address used to access data or the target for instructions. Signup and view all the answers

Which addressing mode allows the address field to specify the address of the address of the operand?

Indirect addressing Signup and view all the answers

What function does the accumulator (AC) serve in the processor's operation?

It holds temporary data for the CPU during computations. Signup and view all the answers

In the context of basic computer organization, what does the instruction cycle fundamentally involve?

Reading and executing instructions in a loop. Signup and view all the answers

Study Notes

Data Transfer Methods

Flags synchronize timing differences between I/O devices and the computer.
FGI (Input flag) starts at 0, indicating the INPR register is ready but empty.
FGO (Output flag) starts at 1, which means the OUTR register is ready to receive data from the AC but is currently empty.

Program Controlled Input/Output

Input operations involve looping until data is ready, using instructions like SKI (Skip if Input) and INP (Input).
Output processes use similar looping with SKO (Skip if Output) and OUT (Output).
Advantages of program-controlled I/O include simplicity and minimal hardware requirement, while it involves continuous CPU engagement, slowing down performance to I/O speeds.

Interrupt Initiated Input/Output

Communication occurs only when data needs to be transferred, prompting an interrupt.
The I/O interface monitors the device readiness, generating an interrupt request to the CPU.
Upon interrupt detection, the CPU pauses its current task to service the interrupt before resuming its prior operation.
IEN (Interrupt-enable flip-flop) can be set/cleared to control interrupt capabilities.

Interrupt Cycle

Functions as a hardware implementation of branching and saving the return address for tasks.
The process repeatedly fetches instructions from memory, executing cycles based on the type of instruction detected.

Fetch and Decode Process

PC (Program Counter) is initially loaded with the first instruction's address, while the SC (State Counter) is cleared.
Post each clock pulse, the SC increments to facilitate instruction execution.

Instruction Types

Register Reference Instructions: Identified by specific bits in the instruction; execution begins with a timing signal.
Memory Reference Instructions: Utilize addresses stored in AR and depend on memory cycles to complete in one CPU cycle. They initiate processing signals T2 and T3.

Memory Reference Operations

AND operation stores the result in AC after reading from the memory address.
ADD operation adds the operand from memory to AC, also tracking carry-out.
LDA (Load to AC), STA (Store AC), BUN (Branch Unconditionally), BSA (Branch and Save Address), and ISZ (Increment and Skip if Zero) provide various control flows and data management mechanisms.

Input-Output and Interrupt Configuration

Input and Output registers are 8 bits long with flags for monitoring state.
Serial data is managed via INPR and OUTR registers, communicating with processing and output devices.

Basic Computer Organization

Comprises a processor and memory capable of storing 4096 words, with each word being 16 bits in length.
Instructions are sequences leading to operation execution in the CPU, involving a systematic fetch and decode mechanism.

Instruction Format and Addressing

Instructions consist of an opcode for the operation and an address for the operands.
Effective address (EA) is directly usable for operand access.
Addressing can be direct or indirect, depending on how the instruction points to data.

Processor Registers

PC tracks the next instruction address using 12 bits.
AR indicates current addressing of memory locations.
DR holds operands found in memory, while the accumulator (AC) serves as a general-purpose register integral for operations.

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Description

Test your understanding of program-controlled data transfer and the flags used for synchronizing I/O device timing with the computer. This quiz explores the initial conditions of input and output registers and their roles in data transfer. Dive into the mechanics of how computers communicate with peripheral devices.