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Automatic Command and Bus Handling Method

IP.com Disclosure Number: IPCOM000117108D
Original Publication Date: 1995-Dec-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Hashimoto, M: AUTHOR [+4]

Abstract

Disclosed is a method which provides automatic command and bus protocol handling on SCSI bus.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 79% of the total text.

Automatic Command and Bus Handling Method

      Disclosed is a method which provides automatic command and bus
protocol handling on SCSI bus.

Using this method, a SCSI device can achieve the following:
  o  Automatic data transfer and disconnection from SCSI bus after
      command receive.
  o  Automatic data transfer and sending status after reselection.
  o  Faster command re-ordering under tagged queuing environment.

      This method is based on a table which is accessed by both
Hardware and micro code.  Each element of the table contains:
  o  Logical Block Address (LBA) of a command
  o  Length of the command
  o  I-T-L-Q.( Initiator - Target - LUN ( Logical Unit Number ) -
      Queue Tag) information for the command
  o  Direction of data transfer for the command

The Figure shows the block diagram of this method:
  1.  Receive a command
      Host Interface Controller ( HIC ) evaluates the validity of a
       command from host.
       HIC also evaluates the validity of the NEXUS for the command.
  2.  Execute the command
      HIC executes the command if there is no command is queued;
i.e.,
       perform cache check and start data transfer if data is
available
       otherwise disconnect bus.
      If command(s) are queued, HIC disconnect bus.
  3.  Register to the table
      HIC stores the table if the command is valid.
  4.  Execute a command from the table
      HIC ex...