Using Cmos Circuitry In Industrial Control - Octagon Systems XE–700 Reference Manual

Please read the following section before installing your product:
Octagon's products are designed to be high in performance while consuming very
little power. In order to maintain this advantage, CMOS circuitry is used.
CMOS chips have specific needs and some special requirements that the user must
be aware of. Read the following to help avoid damage to your card from the use of
CMOS chips.

Using CMOS circuitry in industrial control

Industrial computers originally used LSTTL circuits. Because many PC
components are used in laptop computers, IC manufacturers are exclusively using
CMOS technology. Both TTL and CMOS have failure mechanisms, but they are
different. Described below are some of the failures that are common to all
manufacturers of CMOS equipment.
The most common failures on CPU control cards are over voltage of the power
supply, static discharge, and damage to the serial and parallel ports. On expansion
cards, the most common failures are static discharge, over voltage of inputs, over
current of outputs, and misuse of the CMOS circuitry with regards to power supply
sequencing. In the case of the video cards, the most common failure is to miswire
the card to the flat panel display. Miswiring can damage both the card and an
expensive display.
Multiple component failures: The chance of a random component failure is
very rare since the average MTBF of an Octagon card is greater than 11 years.
In a 7 year study, Octagon has never found a single case where multiple IC
failures were not caused by misuse or accident. It is very probable that multiple
component failures indicate that they were user-induced.
Testing "dead" cards: For a card that is "completely nonfunctional", there is
a simple test to determine accidental over voltage, reverse voltage or other
"forced" current situations. Unplug the card from the bus and remove all
cables. Using an ordinary digital ohmmeter on the 2,000 ohm scale, measure
the resistance between power and ground. Record this number. Reverse the
ohmmeter leads and measure the resistance again. If the ratio of the
resistances is 2:1 or greater, fault conditions most likely have occurred. A
common cause is miswiring the power supply.
Improper power causes catastrophic failure: If a card has had reverse
polarity or high voltage applied, replacing a failed component is not an
adequate fix. Other components probably have been partially damaged or a
failure mechanism has been induced. Therefore, a failure will probably occur in
the future. For such cards, Octagon highly recommends that these cards be
replaced.
Other over-voltage symptoms: In over-voltage situations, the
programmable logic devices, EPROMs and CPU chips, usually fail in this order.
IMPORTANT!
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