Browse Prior Art Database

System Programmable Logic Failsafe Mechanism

IP.com Disclosure Number: IPCOM000123164D
Original Publication Date: 1998-Jun-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 4 page(s) / 120K

Publishing Venue

IBM

Related People

Iachetta, RN: AUTHOR [+1]

Abstract

A failsafe method for ensuring all system programmable devices are programmed prior to product ship is disclosed. If an escape in the manufacturing process fails to program one or more devices, the system will not boot, and a signal indicating the problem will be available.

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

System Programmable Logic Failsafe Mechanism

   A failsafe method for ensuring all system programmable
devices are programmed prior to product ship is disclosed.  If an
escape in the manufacturing process fails to program one or more
devices, the system will not boot, and a signal indicating the
problem will be available.

   Most of the digital circuits in a modern computer system
are non-programmable (i.e. unchangeable) circuits.  These circuits
are inside chips known as ASICs or Gate Arrays.  However, there
generally is some percentage of digital circuits that reside in
"programmable devices", such as PALs, GALs, and Field Programmable
Gate Arrays (FPGA's).  Programmable devices are blank until they are
programmed, and are often programmed with custom digital circuits.
Programmable devices vary in many ways such as the size of the design
they can hold and the speed with which inputs affect outputs or
internal states.

   Programmable devices are more expensive than their
non-programmable counterparts, but are still used in certain
instances where flexibility is important.  Some of the main uses for
programmable devices are:  1) a design where the requirements are not
firm and is likely to change during development -- the greatest
feature of programmable logic is that the device can easily be
reprogrammed with a different design should requirements be changed
or problems with the initial design be found.  2) As specialized glue
logic:  While most of the system can be realized with off-the-shelf
chips, there is a requirement for some specialized glue logic that
does not exist in any of the off the shelf parts -- this specialized
logic can be put in a programmable device rather than go through the
large effort and expense of making a real ASIC just for the extra
glue logic.  3) Bug fixes: Very often during development, bugs are
found in one or more of the main system chips.  Many times these
chips will not be "turned" in time to fix those bugs so the product
must ship with the chips as they are.  A fix can often be placed in a
programmable device that can interface to the broken chip to fix or
avoid the problem.

   Since programmable devices start out blank, they
must be programmed as part of the system or board build process.
Manufacturing processes exist for programming each device with the
correct code.  Most of the time, these manufacturing processes work
fine.  But the authors of this disclosure have noticed that
inevitably there will be escapes from time to time.  One or more of
the programmable devices will inadvertently be left unprogrammed,
i.e. blank.  Most of the time Manufacturing can catch this problem
before  ship time because in most cases the system will fail their
ship criteria tests due to the device being blank.  However, in some
cases, the tests that Manufacturing perfo...