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When a device interrupt signal occurs, how does the processor perform interrupt handling if an interrupt occurs at the N+1th address location?
Hua Phi Vu
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What is an autovector?
In computing, an autovector is an interrupt vector representing a priority level, from which the processor determines the target address.
What is difference between vectored and non vectored interrupts?
Vector interrupt --> when processor directly call the respective isr when interrupt occurs so, address of respective isr is usually save in register. Non interrupt Vector --> In this case when interrupt occurs the processor calls a generic isr and in generic isr uaer has to call respective isr by checking status register.
Why jump instruction is invariably written in the vectored location of an interrupt request?
An interrupt makes the processor to jump to a vectored location in memory where the ISR is written. By observing the vectored locations for various interrupt inputs of 8085, we know that there are only 4 or 8 bytes allocated for ISR. This memory space is not sufficient for writing any code to process an interrupt. So we write a jump instruction that makes the processor jump to a location in user memory and write the ISR starting from that location.Example: suppose there is an interrupt signal to 8085 at RST 6.5. The call location for RST 6.5 is 0034H. The address space available is 4 bytes. So if we write instruction jmp 2300H at 0034H, then we can write ISR in memory locations starting from 2300H.
What is the use of interrupt vector?
An interrupt vector is the memory address of an interrupt handler, or an index into an array called an interrupt vector table or dispatch table. Interrupt vector tables contain the memory addresses of interrupt handlers. When an interrupt is generated, the processor saves its execution state via a context switch, and begins execution of the interrupt handler at the interrupt vector.
What is interrupt vector?
When a processor is interrupted to do a particular task,Program counter should be loaded with the the address of subroutine(task).If the processor automatically generates the address then it is known as vectored interrupt.for example if 8085 microprocessor is interrupted through RST 5.5 pin,then processor multiplies 5.5 by 8 and converts it to Hex address.If user has to provide address of subroutine using CALL instruction then it is known as non vectored interrupt
What is a non-maskable?
A non-maskable interrupt is an interrupt that cannot be blocked, or masked, by the processor. In the 8085, TRAP is such an interrupt. If TRAP goes high and stays high, an interrupt vector sequence at address 24H will occur, and there is nothing the processor can do to prevent that.However, external hardware can accomplish the same thing. In a project that I designed, I needed a fourth single pin interrupt beyond RST5.5, RST6.5, and RST7.5, but I needed it to be maskable, so I built a flip flop in hardware that I could set or reset which would be AND'ed with the interrupt request to generate a maskable TRAP.
How many interrupts in 8085 microprocessor?
The processor has 5 interrupts. They are presented below in the order of their priority (from lowest to highest):INTR is maskable 8080A compatible interrupt. When the interrupt occurs the processor fetches from the bus one instruction, usually one of these instructions:One of the 8 RST instructions (RST0 - RST7). The processor saves current program counter into stack and branches to memory location N * 8 (where N is a 3-bit number from 0 to 7 supplied with the RST instruction).CALL instruction (3 byte instruction). The processor calls the subroutine, address of which is specified in the second and third bytes of the instruction.RST5.5 is a maskable interrupt. When this interrupt is received the processor saves the contents of the PC register into stack and branches to 002Ch (hexadecimal) address.RST6.5 is a maskable interrupt. When this interrupt is received the processor saves the contents of the PC register into stack and branches to 0034h (hexadecimal) address.RST7.5 is a maskable interrupt. When this interrupt is received the processor saves the contents of the PC register into stack and branches to 003Ch (hexadecimal) address.Trap is a non-maskable interrupt. When this interrupt is received the processor saves the contents of the PC register into stack and branches to 0024h (hexadecimal) address.All maskable interrupts can be enabled or disabled using EI and DI instructions. RST 5.5, RST6.5 and RST7.5 interrupts can be enabled or disabled individually using SIM instruction.
What is vector and non vector interrupts?
VECTOR INTERRUPT If the interrupt is assigned to any predefined branching address to its ISR it is termed as vector interrupt. NON VECTOR INTERRUPT If the interrupt is not assigned to any predefined branching address to its ISR it is termed as non-vector interrupt. PRIYAKRISH
What is exhaustive decoding?
Exhaustive Decoding: When all the address lines of the processor are used to specify the address of a memory location, exhaustive decoding is said to be used
What is Non-interrupt vector?
If the interrupt is not assigned any predefined branching address to its ISR it is termed as non interrupt vector
When interrupt occurs where is the address following the current instruction stored?
When an interrupt occurs, the address following the current instruction is stored on the stack.
How does IRQ priority works?
An IRQ is an electrical signal generated by a device needing attention. Usually, it means that some event has occurred such as data being received and ready to use. The IRQ signal is sometimes connected directly to the processor or in some cases to a dedicated interrupt handling circuit. When the processor is told the interrupt has happened it calls the ISR to handle it. The ISR is software that deals with the needs of the device that requested it. Usually, the device is read or some system action is taken to clear the condition that caused the IRQ then the interupt system is reset to make it ready for use again. On most systems, the IRQ signal forces the processor to save it's current program counter so it knows where to return when the ISR is finished, then it jumps to a hard-wired address called the Interrupt Vector where the code for the ISR is placed. At the end of the ISR, the program counter is restored and the program carries on from where it was before the interrupt paused it. Antonio Holl
