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Polling interrupt (CPU keeps polling at regular intervals if a device is ready)
vectored interrupt (I/O device requests for attention)
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A CPU generally handles an interrupt by executing an interrupt service routine?
By checking the interrupt register at fixed time intervals
What is an interrupt How are multiple interrupts dealt with?
An interrupt is a request to execute different code, initiated usually by a hardware condition such as data-ready or operation-complete, but also sometimes initiated by the running program. The processor saves its immediate state, IP and Flags, on the stack and loads a new IP value, effectively doing a CALL sequence to some interrupt service routine. The routine does whatever processing is required, and returns, restoring the running program. Under normal conditions, the interrupt response sequence disables further interrupts, so that recursive entry does not occur. The service routine reenables interrupts just before returning, so that pending or further interrupts can be processed. If multiple interrupt levels are to be supported, such as in the 8085, the interrupt service routine can set the interrupt mask, blocking the level in progress, and then reenable interrupts. This way, a second interrupt on a higher level can be processed while the first interrupt is being processed. On return, the lower level interrupt disables interrupts, restores the mask, and then reenables interrupts prior to return.
What is a TrapHandler?
A trap handler, also called an interrupt handler or interrupt service routine (ISR) is a program that executes when predefined events occur in a computer. There are software and hardware interrupts. An interrupt causes the computer's processor to stop running its current task and immediately run the trap handler to service the interrupt.
What is HISR and LISR in embedded systems context?
HISR: High Level ISR (Interrupt Service Routine) LISR: Low Level ISR
Should any device be allowed to interrupt CPU while another interrupts are being serviced?
It is possible to allow nested interrupts. This is often done when there is a heirarchy of interrupts, some with higher priority than others. In order for this to work, the second interrupt must not be allowed to influence the progress of the first interrupt. We call this being "thread safe". In a nested scheme, an interrupt mask is set so that higher priority interrupts can be permitted, while blocking interrupts of the same or lower priority, and then interrupts are reenabled during the interrupt service routine. At the conclusion of the first routine, interrupts are disabled again, the mask is restored, and the normal interrupt return sequence is executed. In the 8085, this can be supported using the Read Interrupt Mask (RIM) and Set Interrupt Mask (SIM) instructions. While not strictly required, the logical priority is often INTR, RST5.5, RST6.6, RST7.5, and then TRAP, in order of increasing priority.
What is software polling?
When the microprocessor receives an Interrupt Service Request (ISR) on the interrupt line it must determine which of the devices connected to that input sent the request.Software Polling is one method by which it can do so.In Software Polling:A software routine is used to identify the device requesting service. It does so by checking each device to see if it was the one needing service.
What are the similarities between routine and positive messages?
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A CPU generally handles an interrupt by executing an interrupt service routine?
By checking the interrupt register at fixed time intervals
What are the rules to be followed by the interrupt routines in rtos?
1)an interrupt routine must not call any rtos function that bmight block the caller inthe future2)an interrupt routine may not call any rtos function that might cause rtos to switch task unless the rtos knows that an interrupt routine is not a task executive.
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.
Can you call an interrupt routine from your own programs?
Yes you can.
Difference between harware interrupt and internal interrupt?
A hardware interrupt is initiated from a hardware event, such as a byte received from a serial port. It is asynchronous to the running program, i.e. it can occur at any time. An internal, or software, interrupt is initiated by the running program, thus it is under the control of the running program. In the 8085, for instance, the RST instructions are software interrupts. Note, however, that external interrupts can initiate a software RST instruction, so the two events can appear to be the same kind of event. The biggest difference is the handling of the interrupt enable (IE) flag. In the hardware interrupt, the IE flag is turned off when processing the interrupt, and it is turned on right before the interrupt service routine executes the final return instruction. The software interrupt, on the other hand, has nothing to do with IE. As a result, the code must be able to tell the difference.
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.
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.
What is the difference between a goodwill Email and a routine Email?
An email with a good will.
What is interrupt acknowledge?
Interrupt acknowledge is the process of acknowledging a hardware interrupt, obtaining an interrupt vector address, and initiating the interrupt service routine in software. The INTA- (Interrupt Acknowledge) pin has the same timing as RD-, and external hardware is expected to provide an opcode in response to it. In the case of TRAP, RST7.5, RST6.5, and RST5.5, there is no specific interrupt acknowledge cycle like there is for INTR, but everything else is the same.
What is mean by interrupt service routine?
It is a routine in a micro controllers program where the program jumps to after receiving a interrupt on the micro's interrupt pin. Because most micro's can only run one programme at a time, one need a way for the micro to stop doing what it's busy with, to service an outside peripheral that need urgent attention. For instance the micro is running a flashing LED, a push button that one want to use to stop the flashing and start to flash another LED is connected to the interrupt pin of the micro then the program save what it was busy with on a stag and immediately start the interrupt routine.
