SN75LBC970A

SCSI DIFFERENTIAL CONVERTER-CONTROL

SLLS215B – MAY 1995 – REVISED JANUARY 1999

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POST OFFICE BOX 655303

Ended Controller When Used With the

SN75LBC971A Data Transceiver

of 10 Million Data Transfers per Second

Requirements of ANSI Standard EIA-485

and ISO-8482 Standards

with 25 mil Terminal Pitch

22 mA Typ

description

The SN75LBC970A SCSI differential converter-

control is an adaptation of the industry’s first

9-channel RS-485 transceiver, the SN75LBC976.

When used in conjunction with one or more of its

companion data transceiver(s), SN75LBC971A,

the chip set provides the superior electrical

performance of differential SCSI from a single-en-

ded SCSI bus controller. A 16-bit, Fast-SCSI bus

can be implemented with just three devices (two

for data and one for control) in the space-efficient,

56-pin, shrink small-outline package (SSOP) and

a few external components.

In a typical differential SCSI node, the SCSI

controller provides the enables for each external

RS-485 transceiver. This could require as many

as 27 additional terminals for a 16-bit differential

bus controller or relegate a 16-bit single-ended

controller to only an 8-bit differential bus. Using the standard nine SCSI control signals, the SN75LBC970A

control transceiver decodes the state of the bus and enables the SN75LBC971A data transceiver(s) to transmit

the single-ended SCSI input signals differentially to the cable or receive the differential cable signals and drive

the single-ended outputs to the controller.

The single-ended SCSI bus interface consists of CMOS bidirectional inputs and outputs. The drivers are rated

at

±16 mA of output current. The receiver inputs are pulled high with approximately 4 mA to eliminate the need

for external pullup resistors for the open-drain outputs of most single-ended SCSI controllers. The single-ended

side of the device is not intended to drive the SCSI bus directly.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

Copyright

© 1999, Texas Instruments Incorporated

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.

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RSTFLTR

RESET

DSENS

CLK40

GND

AATN –

TEST

AACK –

TIMEOUT

AREQ –

AC/D –

GND

GND

GND

GND

GND

DRVBUS

SDB

AMSG –

AI/O –

ASEL–

NC

ABSY –

NC

ARST –

NC

X2

X1/CLK20

NC

BATN –

BATN+

BACK –

BACK+

BREQ –

BREQ+

BC/D –

BC/D+

GND

GND

GND

GND

GND

BMSG –

BMSG+

BI/O –

BI/O+

BSEL+

BSEL –

BBSY+

BBSY –

BRST+

BRST –

DL PACKAGE

(TOP VIEW)

NC – no internal connection

Terminals 13 through 17 and 40 through 44 are

connected together to the package lead frame and

signal ground.