[time-nuts] Prologix GPIB-USB vs. GPIB-LAN vs. NI was: AW: Prologix GPIB-USB vs. GPIB-LAN

[Chuck Harris]

Hi Mark,

Mark Sims wrote:
> The Prologix adapter has a ++addr command for changing the GPIB address.  You can select different instruments that
> way.
> 
> Unfortunately, the version I looked seems to have a potentially fatal flaw.  When you change the ++addr,  the device
> writes the internal microprocessor EEPROM.  The EEPROM is speced a 1 million write cycles.  If you changed
> instruments at once a second,  in under two weeks the chip could be toast.  My app could have worn out the chip in
> under a day...

Hmmm?  This is what Microchip says:

The data EEPROM is a high-endurance, byte
addressable array that has been optimized for the
storage of frequently changing information (eg.,
program variables or other data that are updated often).
When variables in one section change frequently, while
variables in another section do not change, it is possible
to exceed the total number of write cycles to the
EEPROM (Specification D124) without exceeding the
total number of write cycles to a single byte
(Specifications D120 and D120A).  If this is the case,
then a refresh of the array must be performed.  For this
reason, variables that change infrequently (such as
constants, IDs, calibration, etc.) should be stored in
Flash program memory.

It isn't that the EEPROM wears out, but more that it loses
the values in adjacent cells... unless you refresh them
before 1 million cycles occurs.

All that aside, it isn't clear to me that the ++addr even
writes to EEPROM.

In fact, in the section of my prologix manual where it discusses
the use of EEPROM, it specifically says that the EEPROM stores
configuration information, and that addr is not configuration
information, and must be set as needed.

-Chuck Harris