Correct, I didn't read the NVRAMS.  I didn't have a prom reader/writer that
would handle these devices anyhow and no GPIB interface that worked anymore.
Actually I have two 3458A.  Once I was completely done with the first one
including the cal I didn't even try to put the original NVRAMS removed from
the second meter, just put in the new ones and proceeded to the cal
procedure.

Bill

----- Original Message ----- 
From: "J. L. Trantham" <jlt...@att.net>
To: "'Discussion of precise voltage measurement'" <volt-nuts@febo.com>
Sent: Thursday, August 21, 2014 7:53 AM
Subject: Re: [volt-nuts] HP 3458A Mem test 1 hight. How do youread 32K
memorychips?


> Bill,
>
> Thanks for the insight.
>
> I always thought that I lost my CALRAM data by trying to read the chip in
my
> programmer while the chip was still warm.  What you are saying is that you
> did not try to read your chip, just unsoldered, installed a socket,
plugged
> it back in and the data was corrupted.
>
> Very interesting.
>
> I have done this to three 3458A's and only lost the data on one of the
> units.
>
> This further supports the need to be able to read the contents before
> unsoldering and have that data be able to be used to program a new chip.
>
> Thanks for the insight and I would love to try some programs to do that.
I
> only have Windows systems but I have several USB to GPIB adapter choices,
> PCI to HPIB adapter choices, and RS232 to GPIB adapter choices.
>
> Joe
>
> -----Original Message-----
> From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On
> Behalf Of Bill Gold
> Sent: Thursday, August 21, 2014 9:33 AM
> To: Discussion of precise voltage measurement
> Subject: Re: [volt-nuts] HP 3458A Mem test 1 hight. How do you read 32K
> memorychips?
>
> When I removed the original NVRAM devices and then put in sockets, I
plugged
> the original devices back in just to see if everything worked.  Apparently
> some cal data was lost just desoldering the devices as I got error
messages.
> It really didn't concern me as I intended to completely recal the meter
with
> my local "standards" anyhow.  It was hours before I plugged the original
> devices back in so they were completely at room temp.  My guess was that
> since the date codes were 1992 and I did this in 2010 the batteries were
> almost dead after 18 years and just the shock of desoldering caused "the
> end".
>
> Bill
> ----- Original Message -----
> From: "Mark Sims" <hol...@hotmail.com>
> To: <volt-nuts@febo.com>
> Sent: Wednesday, August 20, 2014 7:20 PM
> Subject: [volt-nuts] HP 3458A Mem test 1 hight. How do you read 32K
> memorychips?
>
>
> > The problem with removing the chip and copying it is the very real
chance
> of glitching the contents in the process.  Much better to make a backup
copy
> first.
> >
> > The 32Kx8 NVRAMS are used for system memory and things like storage of
> user programs and data.
> >
> > Note that the two 32Kx8 devices are form a 16-bit word.  The 2kx8 cal
ram
> is only on the high byte of the data bus.  MREAD returns memory contents
as
> a signed integer value (-32768..32767) in ASCII.
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