Browse Prior Art Database

Dynamic Write Capability for Read Only Storage Using Flash Memory

IP.com Disclosure Number: IPCOM000113592D
Original Publication Date: 1994-Sep-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Feiste, K: AUTHOR [+2]

Abstract

Disclosed is a method to update the contents of a Read-Only Storage (ROS) module using standard I/O load/store instructions and a flash memory.

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

Dynamic Write Capability for Read Only Storage Using Flash Memory

      Disclosed is a method to update the contents of a Read-Only
Storage (ROS) module using standard I/O load/store instructions and a
flash memory.

      A common practice in booting up computer systems is to fetch
instructions and data from a Read Only Storage (ROS) which contains
code to initialize the system and perform various diagnostic tests.
This code is typically burned into a read only EPROM prior to
powering on the system.  During the debug of the computer system and
for field upgrades it becomes necessary to change the contents of the
ROS module.  In the past this required burning a new EPROM and
replacing the old one.  This invention eliminates the need to burn a
new EPROM by providing the capability to write to the ROS.

      In this invention the ROS address space (1 Mbyte) has been
mapped into the I/O address space.  In this address space there is an
8 bit Bus Unit Id (BUID), a 20 bit adapter specific address, and a 28
bit effective address.  When the T bit of a segment register is on
(T=1) data is addressed in an I/O segment.  To read and write data in
this address space the Storage Control Unit (SCU) receives a load or
store instruction from the Fixed Point Unit (FXU).  The segment
register (containing the BUID and adapter specific address) and the
effective address are sent with the instruction as well as the
associated data.  The SCU decodes the BUID for '00'X and th...