Browse Prior Art Database

Data-Driven Approach to Formatter Subsystem in Tape Drive Firmware

IP.com Disclosure Number: IPCOM000114084D
Original Publication Date: 1994-Nov-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 81K

Publishing Venue

IBM

Related People

Fry, SM: AUTHOR [+5]

Abstract

A data-driven method for controling the FORMATTER subsystem in the TAPE DRIVE firmware is disclosed. This method provides a flexible, easy-to-maintain, and easy-to-read code.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Data-Driven Approach to Formatter Subsystem in Tape Drive Firmware

      A data-driven method for controling the FORMATTER subsystem in
the TAPE DRIVE firmware is disclosed.  This method provides a
flexible, easy-to-maintain, and easy-to-read code.

      Read and write operations performed by the Drive Formatter
Subsystem may occur in many different contexts: writing host data in
response to a WRITE command, writing device accessible information,
reading host data in response to a READ command, reading host data in
response to LOCATE or SPACE commands, and reading physical blocks
during an Error Recovery Procedure (ERP) are examples of such
operations.  Each of these contexts has a different set of
requirements which will result in different variations of the read or
write operations.

      Writing separate sets of hard-coded modules to handle each
context-specific operation, is an inflexible and inefficient
approach.  The modules would need to be modified with any change in
the requirements for the operations or new sets of modules may need
to be added.  Writing a single set of hard-coded modules that handle
all variations of the read and write operations would result in
complex and hard to maintain code.

      Providing means of accessing the operational parameters and the
information needed by each module throughout the whole operation is
also a problem.  Accessing shared data is error prone and results in
tight coupling of subsystems.

      A method has been developed to decouple the Formatter subsystem
from the higher level drive subsystem (here referred to as the Volume
subsystem) that is aware of the context of the read or write
operations.  In this method, the operations of the Formatter are
controlled by the data stored by the Volume subsystem in designated
"controls and parameters" areas.  In an Object-Oriented environment,
these areas can be implemented as a set of passive Formatter Control
objects.

      The appropriate data for a specific context can be stored in a
set of spec objects (objects with constant attributes).  Each set
contains all the fixed and defau...