a8259

®
Programmable
Interrupt Controller
July 1997, ver. 1 Data Sheet
Features
n Optimized for FLEX
®
and MAX
®
architectures
n Offers eight levels of individually maskable interrupts
n Expandable to 64 interrupts
n Offers a flexible priority resolution scheme
n Provides programmable interrupt modes and vectors
n Uses approximately 399 logic elements (LEs) in FLEX devices
n Functionally based on the Intel 8259 device, except as noted in the
“Variations & Clarifications” section on page 79
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.
Figure 1. a8259 Symbol
A8259
nEN
DOUT[7..0]
CASOUT[2..0]
CAS_EN
INT
nMRST
CLK
nCS
nWR
nRD
A0
CASIN[2..0]
nSP
nINTA
IR[7..0]
DIN[7..0]
Altera Corporation 57
A-DS-A8259-01