Browse Prior Art Database

Dual Mode SCSI Activity Indicator

IP.com Disclosure Number: IPCOM000123561D
Original Publication Date: 1999-Jan-01
Included in the Prior Art Database: 2005-Apr-05
Document File: 1 page(s) / 39K

Publishing Venue

IBM

Related People

Dixon, R: AUTHOR [+2]

Abstract

Disclosed is a circuit that allows two modes of indicating Small Computer System Interface, (SCSI), I/O activity. Traditionally, SCSI activity has been indicated by the device driver setting and clearing a register. The device driver controlled register controls a Light Emitting Diode, (LED).

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 75% of the total text.

Dual Mode SCSI Activity Indicator

   Disclosed is a circuit that allows two modes of
indicating Small Computer System Interface, (SCSI), I/O activity.
Traditionally, SCSI activity has been indicated by the device driver
setting and clearing a register.  The device driver controlled
register controls a Light Emitting Diode, (LED).

   To maximize performance, it is better to implement a
hardware only SCSI activity indicator.  A special circuit is
implemented to achieve a hardware only SCSI indicator.  The circuit
includes one storage element, (R-S Flipflop) to indicate SCSI
activity.  The Flipflop is set by  the movement of data and cleared
by the corresponding interrupt.

   The movement of data is detected by the SCSI ACK- signal
becoming active.  The interrupt is the SCSI INT-,  signalling the end
of an operation.

   Since the order of operation is first data transfer then
interrupt, the Flipflop ends in the inactive or off state.

   In order to maintain compatibility with legacy software,
the hardware only indicator is combined with the device driver
controlled circuit.  This final circuit therefore supports dual
modes of SCSI activity indication.

   Below is a code fragment of the defining the logic
operation for a Field Programmable Gate Array.  (FPGA).

   The LIGHT_STRB is a decode of the I/O address to the SCSI
activity indicator.  The HDD_LEDFF is a storage element for the
device driver controlled indicator.  The CATCH_FF is the storage
element...