Target Application: Computers Family: FLEX 10K, FLEX 8000, FLEX 6

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Target Application: Computers Family: FLEX 10K, FLEX 8000, FLEX 6

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a8259 Programmable Interrupt Controller MegaCore Function
Target Application:
Computers Family: FLEX 10K, FLEX 8000, FLEX 6000, 9000 7000 Vendor:
Features
Optimized Altera® FLEX® MAX® device architectures Risk-free evaluation with OpenCorefeature available with MAX+PLUS® Functionally based Intel 8259 device
General Description
Altera a8259 MegaCorefunction implements programmable interrupt controller. a8259 initialized microprocessor through eight data lines (din[7.0] dout[7.0]), ncs, nrd, nwr, int, ninta control signals. Figure shows symbol a8259.
Innovation Drive Jose, 95134 Tel. (408) 544-7000 http://www.altera.com
Figure a8259 Symbol
A8259
nMRST nINTA CASIN[2.0] IR[7.0] DIN[7.0] CASOUT[2.0] CAS_EN DOUT[7.0]
Functional Description
Figure shows a8259 block diagram.
Figure a8259 Block Diagram
Interrupt Request Register Priority Resolution In-Service Register
ir[7.0]
ninta casin[2.0] nmrst Interrupt Control Logic
cas_en cas_out[2.0]
Interrupt Vector
din[7.0]
Read/Write Control Logic Initialization/ Command Registers
dout[7.0]
Altera Corporation
A-SB-021-01
ALTERA MEGAFUNCTION PARTNERS PROGRAM
MegaCore
a8259 Programmable Interrupt Controller MegaCore Function
ninta signals provide handshaking mechanism a8259 signal microprocessor. a8259 requests service signal receives acknowledgment acceptance from microprocessor ninta signal. signal applied directly microprocessor's interrupt input. When a8259 receives valid interrupt request ir[7.0] pin, signal goes high. ninta input connected microprocessor's interrupt acknowledgment signal. microprocessor pulses ninta signal twice during interrupt acknowledgment cycle, which tells a8259 that interrupt request been received. Then, a8259 sends highest priority active interrupt type number onto din[7.0] microprocessor acknowledge. inputs used external devices request service, they configured level-sensitive edge-sensitive operation. casin[2.0]and casout[2.0] buses, cas_en pins used implement cascade interface. These pins used when more than a8259 functions interconnected master/slave configuration, expanding number interrupts from a8259 supports several operational commands: priority rotation, interrupt (EOI), special mask mode (SMM), trigger modes, poll command. a8259 operate four different modes: fully nested mode, cascade mode, special fully nested mode, buffered mode.
more information, refer a8259 Programmable Interrupt Controller Data Sheet Microperipheral MegaCore Function Data Book, version
Utilization
Table describes logic cell requirements FLEX architectures.
Table a8259 Logic Cell Requirements
Function
a8259 programmable interrupt controller
FLEX
Variations Clarifications
following characteristics distinguish Altera a8259 function from Intel 8259A device:
master clear provided with a8259 function. clock signal been added, synchronous design rules have been incorporated improve operation reliability. input signals except nmrst ir[7.0] should synchronous clock signal. inputs must asserted clock cycle ensure reliable operation. Bidirectional pins split into separate inputs, outputs, corresponding tri-state control lines. This features makes a8259 compatible with multiplexer scheme used internally design. dout[7.0], casout[2.0], int, cas_en, outputs driven complex logic structures prone glitches. These signals should registered most applications. Automatic slave mode implemented within a8259.
Innovation Drive Jose, 95134 (408) 544-7000 http://www.altera.com
Copyright 1997 Altera Corporation. Altera, FLEX, FLEX 10K, FLEX 8000, FLEX 6000, MAX, MAX+PLUS, MAX+PLUS 9000, 7000, OpenCore, MegaCore trademarks and/or service marks Altera Corporation United States other countries. Other brands products trademarks their respective holders. specifications contained herein subject change without notice. Altera assumes responsibility liability arising application information, product, service described herein except expressly agreed writing Altera Corporation. Altera customers advised obtain latest version device specifications before relying published information before placing orders products services. rights reserved.
Altera Corporation

Target Application: Computers Family: FLEX 10K, FLEX 8000, FLEX 6

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