Browse Prior Art Database

Device Verification State Machine

IP.com Disclosure Number: IPCOM000121909D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 3 page(s) / 104K

Publishing Venue

IBM

Related People

Schwendiman, CA: AUTHOR [+2]

Abstract

Disclosed is an algorithm that provides protection against data loss due to a removable DASD (Direct Access Storage Device) being moved to a different connection location on the host system. This algorithm also verifies the operating characteristics of the device, such as microcode levels and mode select parameters.

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Device

Verification

State

Machine

      Disclosed is an algorithm that provides protection
against data loss due to a removable DASD (Direct Access Storage
Device) being moved to a different connection location on the host
system.  This algorithm also verifies the operating characteristics
of the device, such as microcode levels and mode select parameters.

      The potential problems that this algorithm remedies are the
following: (1) if a device (adapter, controller, or DASD) encounters
an error condition that results in a loss of downloaded microcode,
the device could potentially continue operating with EPROM level
microcode, which obviously is not the quality of the revised
downloadable version, and (2) if two DASDs were to be physically
swapped, then potentially data meant for one DASD could be written to
the other DASD, resulting in data corruption.

      The algorithm consists of a state machine flow where each state
represents the verification of a certain parameter or characteristic.
The states are structured in a hierarchical manner in order to verify
parent devices and then children. The algorithm is designed for use
in the device driver and execution on the interrupt level, thus the
state machine design.  For an example, consider a DASD subsystem
consisting of an adapter card, DASD controllers, and DASD that
support the SCSI protocol (see Fig. 1). Following is a list of steps
taken to verify the entire DASD subsystem (see Figs. 2 and 3).
     Assumptions: The current levels of microcode resident in the
adapter a...