8259A Programmable Interrupt Controller

The 8259A is a programmable interrupt controller which can be used with microprocessors such as 8085 and 8086.

Functions of 8259A-

The 8259A can-

1. vector an interrupt anywhere in the memory map.
2. manage 8 interrupts. This is equivalent to providing 8 interrupt pins on the processor.
3. work in different modes and resolve the interrupts accordingly.
4. mask each interrupt request individually.
5. be programmed to accept level or edge triggered interrupt requests.
6. be expanded to 64 priority levels in cascading mode.
7. read status of interrupts (i.e mask, pending and in-service).
8. used with 8085 or 8086 under different modes.

Pin Diagram- 

Pin Diagram of 8259A

Architecture

Block Diagram of 8259A