CCS 2501 User manual

Owner’s
Manual
Model
2501
Mother
Board
California
Computer
Systems

TABLE
OF
CONTENTS
I
Features
1
II
Operating
Instructions
2
III
Theory
of
Operation
3
IV
Maintenance
4
V
Parts List
5
VI
Schematics
6
Warranty
7
I
FEATURES
-12
Slot
Capability
-All
S-100
Connectors
Included
-Low
Inductance
Interconnect
to
Reduce
Signal
Noise
and Crosstalk
-Active
Termination
of
All
Bus
Lines
to
Further
Reduce
Signal
Noise
and
Line
Reflections
-Distributed
bypassing
of
All
Power
Lines
-Solder
Mask on Both
Sides of
Board
-Silkscreen
of
Reference
Designations
-Simple
Strong
Board
Mounting
-Criss-Cross
Bus
Lines
on
Both
Sides
of
Board
-All
Holes
Plated
Through
-Solder Plated
Circuit
Area
1

II
OPERATING
INSTRUCTIONS
2-1
The
model
2501A
is
packaged
and
shipped
in
a
standard
cardboard
container
with
styrofoam
inserts
to
prevent
damage.
Upon
receipt
of
the
instrument,
a
thorough
inspection
should
be
made
to
reveal
any
possible
shipping
damage.
If,
for
any
reason,
the
instrument
must
be
returned
to
the
factory,
the
original
ship¬
ping
container
should
be used.
2-2
Before
applying
power
to
your
motherboard,
it
must
be
securely
fastened
in
place
using
12
screws,
six
on
each
side.
Care
must
be
taken
that
none
of the
circuitry
on
the
bottom
of
the
board be
allowed
to
contact
ground.
Next,
power
must
be
securely
connected
to
the
board
using
the
connections
supplied.
It
is
vital
that
the
correct
voltages
are
applied
to
the
correct
points
,
or
destruction
to
your
computer
system
will
result.
See
Fig
A
Marked
on
the
circuit
board
are
the
nominal
voltages
to
be
applied
at
each
point.
The
+8
supply
will
normally
be
between
+8
and
+12
depending
upon
the
current
requirements.
The
+16
and
-16
supplies
will
normally
be between
16
and
25
volts
depending
upon
the
load.
DO
NOT
EVER
APPLY
REVERSED
VOLTAGES
OR
EXCESSIVE
VOLTAGES
LEST
IRREPARABLE
DAMAGE
MAY
OCCUR
TO
YOUR
SYSTEM.
100
PIN
SOCKET
J
lllllllllllllllllllllllllllllll
POWER
CONNECTIONS
2

Ill
THEORY
OF
OPERATION
GENERAL
The
model
2501
is
a
12
slot
motherboard
for
use
in
S-100
bus
systems.
It
has
several
design
features
to
optimize
system
operation.
A)
Distributed
bypassing
of
all
power
lines
to
minimize
crosstalk
through
the
power
l
ines
.
B)
Active
termination
of
all
signal
lines
to
minimize
signal
reflections.
C)
Newly
developed
trace
pattern
to
minimize
pulse
ringing.
ACTIVE
TERMINATION
Active
termination
is
achieved
by
returning
all
94
signal
lines
through
separate
330
ohm
resisters
to
a
regulated
+2.4
volts
DC
(See
Fig
B
)
This
means
that
all
signal
lines
are
HIGH
unless
de¬
liberately
pulled
LOW,
and
that all
lines
see
the
same
load
rather
than
being
left
in
an
indeterminate
state.
3

TRACE
PATTERN
If
you
examine
the
trace
pattern
carefully,
you
will
notice
several
features.
First,
all
pins
are
connected
on
each
side
of
the
board.
ie-pin
33
of
every
socket
is
connected
together
on
the
top
of the
board
and
on
the
bottom
of the
board.
This
"double-path"
effectively
halves the
line inductance.
Second,
each
trace
is
maintained
as
wide
as
practicable
further
reducing
line
inductance.
Minimizing
line
in¬
ductance
is
important
as
inductance
causes
ringing
on
signal pulses,
creating
system
errors.
Third,
the
traces
on
the
top
and
bottom
of
the
board
are
in
a
criss-cross
pattern
resulting
in
a
quasi¬
twisted
pair
for
each
signal
line,
minimizing
noise
pickup
and
crosstalk
with other lines.
All
of
this
effort
in
designing
the
trace
pattern
in
conjunction
with the
active
terminations
results
in
signals
with
low
noise,
minimal
ringing,
and
low
line
reflections
along
with
its
concomitant
improved
system
operation.
IV
MAINTENANCE
With
proper
care,
your
model
2501A
motherboard
should
last
a
long
time
giving
a
minimum
of
trouble.
The
unit
should be cleaned
periodically
so that
dirt
and
grime
do
not
build
up
and
short
out
either
the
power
supplies
or
the
signal
lines.
When
doing
this,
be
sure
that
power
is
removed
from
the unit.
This
would
be
a
good
time
to
check
for
loose
hardware and
tighten
as
necessary.
4