[TenTec] updating ROM

Marcus Leatham leatham@nortel.ca
30 Jul 1997 02:24 EDT

In message "[TenTec] updating ROM", Conway Yee writes:

>While it would technically be possible to upgrade the logic board
>so that the ROM is user upgradable off the net, I suspect that it might
>not be done for cost reasons.
>As it stands, the upgrade is switching an EPROM which is a very simple
>matter in terms of design.
>By having a downloadable ROM (of any sort), additional circuitry to
>read and store the data would have to be designed and built.  It hardly
>seems cost effective to design/build circuitry which would rarely (if
>ever) be used.
>tnx es 73 de Conway Yee, N2JWQ

Having just completed designing & testing an upgradable EEPROM
circuit pack for a telephone switch, I can say that today's EEPROMs
do not require a lot of extra circuitry to program.  It is only a 
software routine which does the work.  The EEPROM was a single chip,
organized internally into 8 sectors.  We used it as a 4 + 4 to provide
a "safety backup" copy so that we could program 1/2 of it at a time,
then switch to the new half after we verified the copy was good.
The only other requirement was to have enough RAM to store a temporary
copy of the EEPROM before it was programmed - most products these
days already have sufficient RAM to handle this requirement.

In summary, providing an upgradable EEPROM or "FLASH ROM" ought to
be a very simple task.  If I can do it, so can anyone.  I did the
software / firmware required, including building a switch-compatible 
downloadable EEPROM image and testing the final product, in less 
than six months.  We could not get the product to fail, even when
we yanked the circuit pack out of the chassis during the programming

Go to it, Ten-Tec!

Marcus KR5N

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