Podcast
Questions and Answers
During the instruction cycle, which state directly precedes the 'Operand store' state?
During the instruction cycle, which state directly precedes the 'Operand store' state?
- Instruction operation decoding
- Instruction fetch
- Data Operation (correct)
- Operand fetch
What is the primary characteristic of global interrupt enabling?
What is the primary characteristic of global interrupt enabling?
- It requires special code in the main program.
- It is handled by a specific Interrupt Service Routine (ISR)
- It affects only individual interrupts.
- It affects all maskable interrupts. (correct)
Which type of interrupt is specifically generated by a processor's internal timer?
Which type of interrupt is specifically generated by a processor's internal timer?
- I/O interrupt
- Hardware failure interrupt
- Timer interrupt (correct)
- Program interrupt
In the context of program flow control with interrupts, what is the role of an interrupt handler?
In the context of program flow control with interrupts, what is the role of an interrupt handler?
During the interrupt cycle, what action does the processor take immediately after checking for an interrupt?
During the interrupt cycle, what action does the processor take immediately after checking for an interrupt?
What is the first step in the interrupt cycle when an interrupt is pending?
What is the first step in the interrupt cycle when an interrupt is pending?
In the context of 'Transfer of Control via Interrupts', after the interrupt handler completes its execution, to which point in the user program does control typically return?
In the context of 'Transfer of Control via Interrupts', after the interrupt handler completes its execution, to which point in the user program does control typically return?
What distinguishes program timing with short I/O wait from program timing with long I/O wait when interrupts are involved?
What distinguishes program timing with short I/O wait from program timing with long I/O wait when interrupts are involved?
In the 'Instruction Cycle (with Interrupts) - State Diagram', what state is entered immediately after an interrupt is detected?
In the 'Instruction Cycle (with Interrupts) - State Diagram', what state is entered immediately after an interrupt is detected?
What is the primary advantage of allowing an I/O module to directly write to memory (Direct Memory Access - DMA)?
What is the primary advantage of allowing an I/O module to directly write to memory (Direct Memory Access - DMA)?
Which of the following is NOT a typical step performed when an interrupt is pending?
Which of the following is NOT a typical step performed when an interrupt is pending?
What initiates an I/O interrupt?
What initiates an I/O interrupt?
How does enabling global interrupts affect the system?
How does enabling global interrupts affect the system?
How does Direct Memory Access (DMA) improve system efficiency?
How does Direct Memory Access (DMA) improve system efficiency?
Immediately following the Fetch Next Instruction phase, what action does the system take?
Immediately following the Fetch Next Instruction phase, what action does the system take?
What occurs immediately after 'Instruction operation decoding' in the instruction cycle?
What occurs immediately after 'Instruction operation decoding' in the instruction cycle?
Which scenario necessitates the use of an Interrupt Service Routine (ISR)?
Which scenario necessitates the use of an Interrupt Service Routine (ISR)?
How do 'Program Interrupts' originate?
How do 'Program Interrupts' originate?
What immediate action does the processor take when it detects an interrupt during the 'Check for Interrupt' stage?
What immediate action does the processor take when it detects an interrupt during the 'Check for Interrupt' stage?
In the context of I/O Modules, what role does the processor serve during Direct Memory Access (DMA)?
In the context of I/O Modules, what role does the processor serve during Direct Memory Access (DMA)?
Flashcards
Instruction Cycle
Instruction Cycle
The sequence a computer follows from fetching, decoding, executing, and storing data.
Interrupt
Interrupt
Halts the normal execution of a program to handle an event.
Interrupt Service Routine (ISR)
Interrupt Service Routine (ISR)
A subroutine that is executed when an interrupt occurs.
Global Enabling
Global Enabling
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Local Enabling
Local Enabling
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Program interrupts
Program interrupts
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Timer Interrupt.
Timer Interrupt.
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I/O Interrupts
I/O Interrupts
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Hardware Failure Interrupts
Hardware Failure Interrupts
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I/O Modules
I/O Modules
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Direct Memory Access (DMA)
Direct Memory Access (DMA)
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Study Notes
Instruction Cycle State Diagram
- The instruction cycle consists of instruction fetch, operand fetch, and operand store states.
- After an instruction fetch, the instruction operation is decoded.
- Operand address calculation occurs before both fetching and storing operands.
- Data operation follows operand address calculation during the operand fetch phase.
- Upon completion of an instruction, the next instruction is fetched.
- String or vector data returns for the next.
Interrupts
- No special code is needed in main code.
- Interrupt Service Routines (ISR) handle condition.
- Interrupts can be disabled, with pending interrupts serviced once interrupts are re-enabled.
- Global enabling affects all maskable interrupts.
- Local enabling affects individual interrupts.
Types of Interrupts
- Program interrupts occur due to program execution issues like illegal instructions, arithmetic overflow, division by zero, or memory handling errors.
- Timer interrupts are generated by the processor's internal timers.
- I/O interrupts generated by an I/O controller to request service from elements like keyboard, mouse, NIC, or disk drive.
- Hardware failure interrupts signify error conditions with the hardware.
Program Flow Control
- Program flow involves user programs and I/O programs interacting, with or without interrupts.
- Interrupts can cause short or long I/O waits in program execution.
Interrupt Cycle
- The interrupt cycle begins with fetching the next instruction and executing it.
- Interrupts are checked after each instruction execution.
- If interrupts are disabled, the processor continues with the fetch cycle.
- If interrupts are enabled and an interrupt is pending, the interrupt cycle begins.
Interrupt Cycle (Continued)
- Interrupt processing is added to the instruction cycle.
- The processor checks for interrupts.
- If no interrupt is present, the next instruction is fetched.
- If an interrupt is pending, the current program's execution is suspended.
- The context (registers, program counter (PC), flags) is saved on the stack.
- The PC is set to the starting address of the interrupt handler routine.
- The interrupt is then processed.
- Finally, the context is restored, and the interrupted program continues.
Transfer of Control via Interrupts
- Describes how interrupts cause the transfer of control between the user program and the interrupt handler.
Program Timing
- Program timing described for short and long I/O waits without and with interrupts.
Instruction Cycle with Interrupts
- Similar to the basic instruction cycle but includes interrupt check and interrupt handling states.
- If an interrupt is detected, the process moves to interrupt handling.
- If no interrupt is detected, the process continues to the next instruction.
I/O Modules
- I/O modules occasionally need attention for data transfers.
- Processors can transfer data back and forth with devices like memory.
- Processors might allow I/O modules to write directly to memory using Direct Memory Access (DMA).
- An interrupt occurs when DMA is complete.
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