Browse Prior Art Database

Multiple Small Computer System Interface Command Arrangement

IP.com Disclosure Number: IPCOM000114783D
Original Publication Date: 1995-Jan-01
Included in the Prior Art Database: 2005-Mar-29
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Ishibashi, K: AUTHOR [+3]

Abstract

Disclosed is a method for managing multiple Small Computer System Interface (SCSI) commands and phases for Hard Disk Drive (HDD) with SCSI interface. Multiple sequences for receiving a command are automatically managed and necessary parameters for executing a command are arranged as a table.

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Multiple Small Computer System Interface Command Arrangement

      Disclosed is a method for managing multiple Small Computer
System Interface (SCSI) commands and phases for Hard Disk Drive (HDD)
with SCSI interface.  Multiple sequences for receiving a command are
automatically managed and necessary parameters for executing a
command are arranged as a table.

Generally the SCSI sequence for receiving a command are as follows.
  1.  Arbitration - Selection - Identify message('C0'h) - Command
  2.  Arbitration - Selection - Identify message('C0'h) - Queue tag
       message - Command
  3.  Arbitration - Selection - Identify message('80'h) - Command
  4.  Arbitration - Selection - Command

      These sequences are handled automatically by hardware
(Sequencer).  The sequencer arranges the necessary parameters (e.g.,
Initiator ID, Identify message, Queue tag message and Command
Descriptor Block) as a table to the Sector buffer.  Fig. 1 shows the
Block diagram of the data flow.  The SCSI parameters (message,
command..) from SCSI bus are stored to the sector buffer via DMA bus.
Fig. 2 shows the example of the table format.

      This method not only decreases the amount of microprocessor
intervention, but also reduces the overall SCSI command overhead.