DS2109

022698 2/10

REFERENCE DOCUMENTS

SCSI–2 (X3.131–1994)

SCSI–3 Parallel Interface (X3T10/855D)

Available from: Global Engineering Documents

15 Inverness Way East

Englewood, CO 80112–5704

Phone: (800) 854–7179,(303) 792–2181

Fax: (303) 792–2192

PnP SCSI Specification

PnP ISA Specification

PnP BIOS Specification

PnP Option ROM Specification

Available from: Plug and Play forum on

CompuServe (Go plugplay).

FUNCTIONAL DESCRIPTION

The DS2109 is designed to be a single chip termination

subsystem for use in PnP SCSI systems, Figure 1.

When embedded on a host bus adapter or mother-

board, the DS2109 can automatically sense the ter-

mination status of the SCSI bus and attach or isolate its

resistors as needed to maintain proper bus termination.

External and internal active termination can be provided

by the DS21S07A.

DS2109 APPLICATION ENVIRONMENT Figure 1

PERIPHERAL

SUBSYSTEM

EXTERNAL

TERMINATOR

(TWO DS21S07A)

DS2109 AUTOMATIC

EXIT–POINT TERMINATOR

HOST SCSI

PROTOCOL CHIP

SCSI

PERIPHERAL

DEVICES

INTERNAL

TERMINATOR

(TWO DS21S07A)

SCSI INTERNAL

CABLES

SCSI EXTERNAL

CABLE

50–POSITION

HIGH DENSITY

CONNECTORS