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Delayed or Rejected Command Execution Mechanism

IP.com Disclosure Number: IPCOM000104641D
Original Publication Date: 1993-May-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Mathis, JR: AUTHOR

Abstract

In a communication subsystem the normal activity of the link is asynchronous to the execution of instruction by the processor or microprocessor which is providi control functions for that link. The present mechanism provides the system with the ability to delay execution of a Stop command if the adapter is engaged in a productive transaction when the Stop command is received or to reject a command which is inappropriate for the current link conditions without causing a link malfunction, link error or data integrity problem.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 55% of the total text.

Delayed or Rejected Command Execution Mechanism

      In a communication subsystem the normal activity of the link is
asynchronous to the execution of instruction by the processor or
microprocessor which is providi control functions for that link.  The
present mechanism provides the system with the ability to delay
execution of a Stop command if the adapter is engaged in a productive
transaction when the Stop command is received or to reject a command
which is inappropriate for the current link conditions without
causing a link malfunction, link error or data integrity problem.

      Stop commands may be delayed by setting a Command Pending
status flag to indicate that a command has been received from the
processor unit that cannot be immediately executed by the channel
hardware.  If a Stop channel command is issued while a command
pending status flag is set, the action taken by the channel will
depend upon the prevailing conditions and state of the channel at t
time of receipt.

      A command rejection may be caused by issuing an improper
command for the conditions present in the channel (synchronous to
program execution) or due to link events which are asynchronous to
program execution.  The action taken by the channel will depend upon
the conditions present in the channel when the command is issued and
whether or not the conditions causing the Command Reject is
synchronous or asynchronous in nature.

      For example, a Command Reject due to an asy...