Browse Prior Art Database

Ros Code Integrity Protection

IP.com Disclosure Number: IPCOM000102536D
Original Publication Date: 1990-Nov-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 74K

Publishing Venue

IBM

Related People

McClannahan, GP: AUTHOR [+2]

Abstract

A method for maintaining and switching to a redundant copy of non-volatile storage is described. It is useful for processor-based systems which must IPL from the nonvolatile storage. The method described can be used for all types of storage to provide increased reliability, but it is most useful for FEPROM (Field Erasable, Programmable, Read-Only Memory or Flash Memory) storage.

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

Ros Code Integrity Protection

       A method for maintaining and switching to a redundant
copy of non-volatile storage is described.  It is useful for
processor-based systems which must IPL from the nonvolatile storage.
The method described can be used for all types of storage to provide
increased reliability, but it is most useful for FEPROM (Field
Erasable, Programmable, Read-Only Memory or Flash Memory) storage.

      In the system (illustrated in the figure), there is a
microprocessor, an interface module and two FEPROMs.  The function of
the interface module is to convert the control signals from the
processor into compatible control signals for the FEPROMs if needed
and to provide the logic required to switch between the two FEPROMs.
FEPROMs have the characteristic that in order to modify any part of
their contents, the entire contents must be erased.  This means that
if the process of erasing and rewriting the contents is interrupted
by an external event, such as a system reset or power failure, the
contents of the device will be lost. Once this happens, it is no
longer possible to IPL the processor.  If the processor is used to
rewrite the FEPROM, as it is in many systems, the system will no
longer function and will require service or replacement.

      In order to prevent a loss of the information and IPL code
contained on the FEPROM or other storage devices, a second storage
unit is added.  Initially, the second unit will contain an exact copy
of the data stored in the first.  Also, a timer and logic to reset
the processor is added to the interface module.  When the system is
turned on or reset, the processor will begin to load instructions
...