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When execution id going to service an interrupt what happens to stack and what are the registers saved?
Wiki User
∙ 11y ago
The stack will store the return address and the accumulator and flags.
Wiki User
∙ 11y ago
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What is interrupt service deadline?
It is defined as maximum permissible interrupt latency plus execution interval of the ISR.
What happens when interrupts comes?
Interrupt handler is responsible for following functions:- Determine the interrupt source. Determine the service routine to serve the interrupt source.
What is interrupt mechanism?
At the beginning of each FDE cycle, each bit in the interrupt register is checked in turn. This register is a special register in the CPU that takes note of when an interrupt has happened. Each bit in the register represents a different kind of interrupt. If a bit has been set, that would indicate an interrupt has happened! The CPU has to decide whether to service the interrupt immediately, or leave it till later. For example, if 2 interrupts have happened at the same time, one of them has to wait! Which one? That depends upon which one is the least important! Some interrupts are more important than others and so need to be done before others. What about the situation where one interrupt is currently being serviced by the CPU and another happens? Again, it depends on how important the new interrupt is compared to the one already being done. If it is more important, then the cpu will want to service it immediately. When the CPU decides to service an interrupt, it stops processing the current job, 'pushing' the contents of its registers onto the stack. This would include, for example, the contents of the Program Counter and the accumulator. The CPU is now free to work on another piece of software but can return to what it was doing after the interrupt has been serviced because it has saved where it was. It then transfers control to the interrupt handling software for that type of interrupt using the vectored interrupt mechanism. When it has finished servicing the interrupt, the contents of the stack are 'popped' back into the appropriate registers and the CPU continues from where it left off before the interrupt happened.
How long can the INTR signal stay high?
The INTR pulse can remain high until the interrupt flip-flop is set by the EI instruction in the service routine. If it remains high after the execution of the EI instruction, the processor will be interrupted again, as if it were a new interrupt.
Service of execution?
That's a service for acting out the execution of service. Elizabeth
What is key difference between a trap and interrupt?
An interrupt is generally initiated by an I/O device, and causes the CPU to stop what it's doing, save its context, jump to the appropriate interrupt service routine, complete it, restore the context, and continue execution. For example, a serial device may assert the interrupt line and then place an interrupt vector number on the data bus. The CPU uses this to get the serial device interrupt service routine, which it then executes as above.A trap is usually initiated by the CPU hardware. When ever the trap condition occurs (on arithmetic overflow, for example), the CPU stops what it's doing, saves the context, jumps to the appropriate trap routine, completes it, restores the context, and continues execution. For example, if overflow traps are enabled, adding two very large integers would cause the overflow bit to be set AND the overflow trap service routine to be initiated.
When interrupts occur which registers are pushed and popped from the stack?
The registers that are pushed and popped from the stack during interrupt servicing depend on the processor architecture and whether or not a specific register is used by the service routine. Automatically pushed and popped registers include the program counter, flags, and (often) the accumulator. Manually pushed and popped registers include any others that are used, i.e. modified, by the routine. Some programmers push and pop all registers, but that can be unnecessary and wasteful (of time) if some registers are not modified.
What is the use of RST?
RSTn(0-7) is software interrupt & RST(7.5,6.5,5.5) are INTEL's 8085 maskable interrupts their priority is respectively 7.5,6.5,5.5.RSTn.5 is hardware intterrupt and it is controlled by the external pin available on the chip of 8085. it is used to interrupt the microprocessor from its normal execution and tends to execute some ISR(interrupt service routine)
A CPU generally handles an interrupt by executing an interrupt service routine?
By checking the interrupt register at fixed time intervals
What happens when processor is attending an interrupt if it gets another interrupt?
The response to another interrupt request during servicing of an interrupt depends on the setting of the interrupt enable flag and/or the interrupt mask. If the interrupt service routine is thread safe, it will process correctly. More probably, problems will arise so the proper procedure is to either set the interrupt mask (8085) to not allow this or lower priority interrupts before reenabling interrupt, or to leave interrupts disabled until this iteration is complete. If interrupts are disabled or masked, a subsequent interrupt will be posted but not processed until the first is completed.
Why used interrupts?
An interrupt is a signal from hardware (h/w interrupt) or software (s/w interrupt) to indicate the occurence of an event. It indicates the need of a change in execution. Interrupt handling or servicing of the interrupts depends upon the design of the operating system. A routine which will be called for servicing the interrupt is known as interrupt service routine or ISR and the request for the ISR through an interrupt is known as interrupt request or IRQ. Interrupt is a mechanism used for implementing the multitasking concept. It will use the concept of context switching, for servicing the request.
When devices interrupt occurs how does the processor determine which device issued the interrupt?
It's pretty simple. First, the processor must determine which interrupt occurred. On simple hardware setups, you may already know this just by which interrupt handler was called. On more complex hardware, you may have to read status registers in the interrupt controller. Second, the processor has to look up which devices are capable of asserting that interrupt. On simple hardware, generally there is only one device that can trigger each interrupt and this is determined by the way the device is wired. On more complex devices, this may be determined by software and the processor may have to consult tables that were created during the boot process. Third, the processor must determine which of those devices actually asserted the interrupt (if there's more than one). This is typically done by the driver for each device which generally just asks the device if it triggered an interrupt. Most devices have status registers that either directly tell you whether it caused an interrupt or tell you whether the device needs service which was the point of the interrupt anyway.
