Browse Prior Art Database

Adapter for Operating 16-Bit Devices on 8-Bit Small Computer System Interfaces

IP.com Disclosure Number: IPCOM000115904D
Original Publication Date: 1995-Jul-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 126K

Publishing Venue

IBM

Related People

Andresen, ME: AUTHOR [+4]

Abstract

Disclosed is an architecture allowing the intermixture of 8- and 16-bit Small Computer System Interface (SCSI) devices on the single 50-position ribbon cable of an internal subsystem, and an implementation of this architecture in the form of a SCSI adapter.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Adapter for Operating 16-Bit Devices on 8-Bit Small Computer System
Interfaces

      Disclosed is an architecture allowing the intermixture of 8-
and 16-bit Small Computer System Interface (SCSI) devices on the
single 50-position ribbon cable of an internal subsystem, and an
implementation of this architecture in the form of a SCSI adapter.

      Current methods of 8-bit SCSI cabling do not allow the
inter-mixture of 16-bit devices and 8-bit devices on a single
internal 8-bit cable system, unless a unique, manually-prepared cable
is provided.  Current 8-bit SCSI subsystems typically have internal
cables connected in a daisy chain.  Each the internal cables consists
of 2x25 connectors with 50 pins on 0.10-inch centers, connected by a
molded flat ribbon cable having 50 wires on 0.05-inch centers.  Each
8-bit device has a mating 2x25 connector.  In the new 16-bit SCSI
internal cabling systems, the connector is a 2x34 "D"-shaped unit
having 68 pins are on 0.05-inch centers.  These connectors are
themselves connected by a ribbon cable having wires on 0.025-inch
centers.  This means that the old connectors will not work on the new
ribbon cable and vice versa.

      Other proposals for dealing with this situation either require
the use of two cabling systems running through the computing system
from two connectors on the SCSI adapter card (a total of 50 + 68 =
118 pins), or the use of a 68-position ribbon cable which is
mechanically serrated and hand aligned at pre-arranged positions to
accept the 16-bit connectors.  Attaching connectors in this latter
way is a tedious operation with high costs and low yields.
Furthermore, the need to decide on the prearranged positions on the
cables for the 16-bit devices makes various system cables
individually unique, removing the flexibility otherwise allowing
customers to arrange devices within the system as needed.

      The presently disclosed interconnection method includes the use
of an adapter configured so that the signals required by the 8-bit
interface are properly routed from the SCSI 8-bit male connector to
the SCSI 16-bit "D"-shell connector, so that the grounds are properly
routed, and so that certain incompatibilities between the previous
and new versions of SCSI with regard to termination power are
resolved.  Furthermore, the thickness and height of the adapter are
minimized to allow use in current systems without causing mechanical
interferences.  Termination is provided on the high-order bus lines
not used...