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Multiple-speed Selection for a Small Computer System Interface

IP.com Disclosure Number: IPCOM000109703D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Keener, D: AUTHOR [+2]

Abstract

This article describes a technique which allows a small computer system interface (SCSI) controller to be programmed to operate at a unique speed without affecting the SCSI bus operation. This is done via the use of the power-on reset signal and the setup signal which enter the SCSI controller module.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 67% of the total text.

Multiple-speed Selection for a Small Computer System Interface

       This article describes a technique which allows a small
computer system interface (SCSI) controller to be programmed to
operate at a unique speed without affecting the SCSI bus operation.
This is done via the use of the power-on reset signal and the setup
signal which enter the SCSI controller module.

      In order to create a SCSI module which is flexible enough to
work in multiple systems, there is a need for the interface to the
system bus to be able to handle more than one system speed.  However,
the system speed does not change once a system is powered on;
therefore, the SCSI module needs to be able to be programmed at
power-on time to the current system speed.  The technique of this
disclosure allows the programming of the module without the use of
special input pins which affect the packaging size of the module.

      A SCSI controller module containing a system interface to the
local processor bus contains a power-on reset input, a setup input,
an oscillator input for the SCSI handshaking operation, an oscillator
input for the microcontroller module.  The system interface speed
needs to be able to work off either the SCSI handshaking oscillator
or the microcontroller oscillator.  This decision on which speed to
use can be programmed by the user via the setup input.  The user can
pull the setup pin either high or low at power-on time, and when
power-on reset goes inactive, the...