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When an interrupt is serviced then what happens if another interrupt is raised?
It depends on the CPU architecture. Most modern CPUs support several levels of interrupts ranging from high priority to low. If the first interrupt that occurred was a high priority, then a lower priority one occurs, the high priority will continue to execute until it is done, then the the CPU will immediately jump to the lower one. Conversely, if the lower priority interrupt occurred first, it will be interrupted until the higher interrupt is serviced. For 80x86 series processors, do not confuse priority with vector. You may remember in the older days interrupt 13 belonging to the hard drive, and interrupts 3 and 4 being part of the serial port. This is not a function of the CPU but of the interrupt controller. The function of this device is beyond the scope of my answer here. 80x86 has 2 interrupt sources: maskable and non-maksable. Think of the non-maskable as the higher priority and the maskable as the lower. Most peripherals use the maskable interrupt line. Although a few, often functions of the BIOS, Fault, or Paged/Protected mode make use of the non-masked interrupt.
When an operating system receives an interrupt from the printer and pauses the CPU?
Processor management is the operating system that receives and interrupt from the printer and pauses the CPU.
What is the meaning of maskable hardware interrupt?
A maskable hardware interrupt is one that can be disabled, or masked, by instructions in the CPU. In the 8085, all interupts except TRAP and (software) RST N can be masked by disabling interrupts, and RST7.5, RST6.5, and RST5.5 can be individually masked with the SIM (Set Interrupt Mask) instruction. In general, you leave interrupts disabled until one instruction before returning. In the case of the RST*.5 interrupts, you can mask it during interrupt processing and then enable interrupts, allowing other levels to interrupt you again. At the conclusion of the interrupt routine, you would disable interrupts, restore the mask, enable interrupts, and return. If you use this method, you can choose the nesting priority as desired. You determine what mask to set using the RIM (Read Interrupt Mask) instruction and then do bit manipulation before using SIM.
A CPU generally handles an interrupt by executing an interrupt service routine?
By checking the interrupt register at fixed time intervals
What is non maskable interrupt interrupt?
Non Maskable interrupts (such as those generated by power failure) cannot be blocked by the CPU. Maskable interrupts are common device interrupts such as disk/network adapters interrupts which can be blocked by the CPU.
What is an interrupt and how are multiple interrupts dealt with?
An Interrupt is a signal that goes into a microprocessor that tells it something has happened that needs attention. There are generally dedicated pins on the microprocessor, often called "Int" (for Interrupt) and "NMI" (for Non-Maskable Interrupt). For a microprocessor, an interrupt signal is like the bell on a telephone is for you; it's a notice that you should stop what you are doing now and deal with this issue that has come up. Exact procedures for dealing with an interrupt vary from one microprocessor to another; generally, the microprocessor puts out a signal that says "Where should I go, then?" and a piece of hardware, the Interrupt Controller, then responds with a signal that tells it which condition has happened. The processor then starts processing the indicated piece of code, and that piece of code handles the condition. The Interrupt Controller often handles setting priority for interrupts, accepting a number of signals (often four), and setting priorities on each. It will trigger another interrupt in the middle of processing one if the new interrupt is a higher priority than the one that is already being processed, or will hold on to the lower priority one until the CPU is finished with a higher-priority one. The CPU can often "disable interrupts" when it is doing something time-critical. At such times, the only interrupt that can occur is the Non-Maskable Interrupt, which is generally reserved for critical error conditions that have to be dealt with immediately no matter what else is going on.
Why are interrupt required?
Interrupts are required in order to get the attention of the CPU. A CPU typically has two interrupt lines. One is the nonmaskable interrupt line (NMI). That is used in the case of critical errors, since this interrupt cannot be ignored. The other one is the regular interrupt line. That is used by hardware devices and certain software to get the attention of the CPU. When you move a mouse, for instance, that creates both a hardware and software interrupt. So the CPU would then process the mouse driver code and move the cursor, then get back to what it was doing.
When the mouse initiates a hardware interrupt to the CPU how does the CPU know?
The CPU does not "know" it is not a thinking being. What happens is that the interrupt flag ( a binary true or false register) is detected by the operating system which is being executed by the CPU and the code of the operating system runs a routine in response.
Which setting must a device have in order to interrupt the CPU?
IRQ
What is it called when a device requests the CPU to perform a task?
interrupt controller
HOW IS SOFTWARE INTERRUPT INITIATED?
Interrupt signals initiated by programs are called software interrupts. A software interrupt is also called a trap or anexception. A signal informing a program that an event has occurred. When a program receives an interrupt signal, it takes a specified action (which can be to ignore the signal). Interrupt signals can cause a program to suspend itself temporarily to service the interrupt. Interrupt signals can come from a variety of sources. For example, every keystroke generates an interrupt signal. Interrupts can also be generated by other devices, such as a printer , to indicate that some event has occurred. PCs support 256 types of software interrupts and 15 hardware interrupts. Each type of software interrupt is associated with an interrupt handler -- a routine that takes control when the interrupt occurs. For example, when you press a key on your keyboard, this triggers a specific interrupt handler. The complete list of interrupts and associated interrupt handlers is stored in a table called the interrupt vector table , which resides in the first 1 K of addressable memory.
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.
