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NM95MS18

Plug & Play Front-end device for ISA-Bus Systems (Supports Windows®-NT, UNIX® and legacy systems)

Fairchild Semiconductor 

Functional Description

As mentioned above, NM95MS18 can be configured for either

Plug-n-Play environment or Non-Plug-n-Play environment. Under

either interface, NM95MS18 provides a choice from 2 operating

modes, viz, DMA Mode or Extended Interrupt Mode offering

additional flexibility in selecting a suitable set of features for a

particular application. Mode selection is made by setting ap-

propriate bits in the "I/O DECODE QUALIFICATION" register in

onboard EEPROM. Refer to "NM95MS18 User's Guide" for more

detail. Each of these modes is explained below.

DMA Mode

In the DMA Mode, NM95MS18 provides the following features:

1. Two programmable I/O chipselects (IOCS0*and IOCS1*)

each of which can be set to be decoded off of ISA address

SA[0:11] and IORD*/IOWR* or just by SA[0:11]. In addition

IOCS1* signal can be internally Wire-ANDed with IOCS0*

signal, to provide "Output Enable" signal for ISA bus data

buffers.

2. Two local Interrupt request signals switchable to any six IRQ

channels on the ISA Bus. Choice of actual ISA IRQ channels

selected is user dependent. Also the type of the six IRQ

outputs can be independently set to be either standard TTL

type or Open-Drain type. Selecting Open-Drain type allows

interrupts to be shared on the ISA bus.

3. One local DMA request signal switchable to any two DMA

channels on the ISA Bus. Choice of actual ISA DMA

channels selected is user dependent.

Following figure shows a typical system block diagram of

NM95MS18 used in DMA Mode.

DMA Mode

RSTDRV

OSC

IORD*

IOWR*

AEN

SA[0:11]

SD[0:7]

IRQOUT[0:5]

ISADRQ[0:1]

ISADACK[0:1]

ON

OFF

DMA Mode

GND

Switch

VCC

10K

IOCSO

IOCS1

NM95MS18

(DMA Mode)

10K

IRQIN[0:1]

DRQIN

DACKOUT

SOUND

Controller

DS500033-6

Extended Interrupt Mode

(Supports PC-95/PC-97

Requirements)

In Extended Interrupt Mode, NM95MS18 provides these features:

1. Three programmable I/O chipselects (IOCS0*, IOCS1* and

IOCS2*) each of which can be set to be decoded off of ISA

address SA[0:11] and and IORD*/IOWR* or by just ISA

address bus only. In addition IOCS1* and IOCS2* signals

can be internally Wire-ANDed with IOCS0* signal, to provide

"Output Enable" signal for ISA bus data buffers.

2. One on-board Interrupt request signals switchable to any

eight IRQ channels on the ISA Bus. Choice of actual ISA

IRQ channels selected is user dependent. Also the type of

the eight IRQ outputs can be independently set to be either

standard TTL type or Open-Drain type. Selecting Open-

Drain type allows interrupts to be shared on the ISA bus.

Following figure shows a typical system block diagram of

NM95MS18 used in Extended Interrupt Mode.

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