General Description

The Altera® a8259 MegaCore™ function is a programmable interrupt controller. The a8259 can be initialized by the microprocessor through eight data bus lines (din[7..0] and dout[7..0]), and the ncs, nrd, nwr, int, and ninta control signals. Figure 1 shows the symbol for the a8259.

Features

■ Optimized for FLEX® and MAX® architectures

■ Offers eight levels of individually maskable interrupts

■ Expandable to 64 interrupts

■ Offers a flexible priority resolution scheme

■ Provides programmable interrupt modes and vectors

■ Uses approximately 399 logic elements (LEs) in FLEX devices

■ Functionally based on the Intel 8259 device, except as noted in the “Variations & Clarifications” section on page 79