Browse Prior Art Database

Method for Function Change of Read Only Memory Program

IP.com Disclosure Number: IPCOM000114329D
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Asano, H: AUTHOR [+4]

Abstract

This article discribes methods for function change of Read Only Memory (ROM) program which is used to control data read/write for Hard Disk Drive (HDD). These methods can enable to change functions of ROM program stored in ROM device which cannot be replaced in the field.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 80% of the total text.

Method for Function Change of Read Only Memory Program

      This article discribes methods for function change of Read Only
Memory (ROM) program which is used to control data read/write for
Hard Disk Drive (HDD).  These methods can enable to change functions
of ROM program stored in ROM device which cannot be replaced in the
field.

      Fig. 1 shows Method 1.  At check points of ROM program, the
processor checks the vector table which is built on Random Access
Memory (RAM) with a set of change bit, target address and designated
RAM address.  When ROM program is required to change, vector table is
revised.  The processor sets target address, if change bit is on, to
a comparator which is always checking bus address and sends interrupt
signal to processor if bus address equals to the target address.
This interrupt signal is the trigger to change instructions on RAM
area, processor will branch to ROM area.

      This method can enable not to replace ROM device for function
change of ROM program when ROM program requires function changes.
This method can also minimize size and running time of RAM program
because only ROM program to be changed is set on RAM area.

      Fig. 2 shows Method 2.  At check points of ROM program, the
processor checks the vector table which is built on RAM with a set of
change bit and disignated RAM address.  When ROM program is required
to change, vector table is revised.  The processor will branch to
designated RAM address...