Specifications
• Backplane
Quality
-- Be sure
to
use a high quality backplane having minimal signal
crosstalk. Use
of
power and ground planes, and ground guard traces between bus sig-
nals is recommended
• Reset
DegUtGhing
Some PC
bus
expansion cards have asynchronous I I L inputs that
are
. especially
wlnerable
to cable noise
and
crosstalk.
In
particular, the active high
RESET
line is one
to
watch out for.
If
this
signal
is found to
be
susceptible, a 200pf
to
SOOpf
capacitor connected between
the
RESET
signal
and ground can
be
used to pre-
vent false expansion card resets. This
RESET
deglitching capacitor is included
on
the
Ampro MiniBackplanes.
2.6.4 Exparislon
Bus
Connector
Pinouts
Tables 2-25A and 2-25B indicate the pinout and
signal
functions
of
the
signals
on
the
board's
PC Expansion Bus connectors.
Further
information
about
these signals is available
in
numerous publications, including
the
mM
technical reference manuals for the
PC
computer,
and from
the
reference documents listed in
the
beginning
of
Chapter
4.
The board's
PC
Expansion Bus header connector (J9)
pins
have been numbered differently
from
the
other
header
connectors
on
the
board,
so
that
they correspond
to
the
scheme
normally used
on
PC
bus edgecard connectors. The even numbered pins correspond to the
"B"
row
of
the
PC
bus; and the
odd
numbered pins correspond to
the
"A"
row (e.g.,
J9
pin
I is
labeled "BI ").
The
fll'St
62
pins
of
J9 (beginning at
Al
and
BI)
are
the
ones which correspond
to
the 62 conductors-of
the
PC
Expansion Bus
of
the
PC
backplane.
The
last two pins
are
spare grounds.
Note that
the
Little
BoardlPC
does not generate + / - 12VDC
or
-SVDC for
the
PC
Expan-
sion Bus.
If
devices
on
the
PC
Expansion Bus require these voltages, they can
be
supplied to
the
PC
Expansion Bus connector from the board's utility connector (J4).
2-28