An End Of Interrupt is a signal sent to a Programmable Interrupt Controller

Programmable Interrupt Controller

In computing, a programmable interrupt controller is a device that is used to combine several sources of interrupt onto one or more CPU lines, while allowing priority levels to be assigned to its interrupt outputs. When the device has multiple interrupt outputs to assert, it will assert them in...

 (PIC) to indicate the completion of interrupt processing for a given interrupt

Interrupt

In computing, an interrupt is an asynchronous signal indicating the need for attention or a synchronous event in software indicating the need for a change in execution....

. An EOI is used to cause a PIC to clear the corresponding bit in the In-Service Register (ISR), and thus allow more interrupt request

Interrupt request

The computing phrase "interrupt request" is used to refer to either the act of interrupting the bus lines used to signal an interrupt, or the interrupt input lines on a Programmable Interrupt Controller...

s of equal or lower priority to be generated by the PIC.

EOIs may indicate the interrupt vector

Interrupt vector

An interrupt vector is the memory address of an interrupt handler, or an index into an array called an interrupt vector table that contains the memory addresses of interrupt handlers...

 implicitly, or explicitly. An explicit EOI vector is indicated with the EOI, whereas an implicit EOI vector will typically use a vector as indicated by the PICs priority schema. For example, the highest vector in the ISR. Also, EOIs may be sent at the end of interrupt processing by an interrupt handler

Interrupt handler

An interrupt handler, also known as an interrupt service routine , is a callback subroutine in microcontroller firmware, operating system or device driver whose execution is triggered by the reception of an interrupt...

, or the operation of a PIC may be set to auto-EOI at the start of the interrupt handler.

See also

• Interrupt
  Interrupt
  In computing, an interrupt is an asynchronous signal indicating the need for attention or a synchronous event in software indicating the need for a change in execution....
  
  
• Programmable Interrupt Controller
  Programmable Interrupt Controller
  In computing, a programmable interrupt controller is a device that is used to combine several sources of interrupt onto one or more CPU lines, while allowing priority levels to be assigned to its interrupt outputs. When the device has multiple interrupt outputs to assert, it will assert them in...