Theory
of
Operation 2-51
Printer and Keyboard
The
motherboard
distributes
power
to the printer
and
the keyboard. A ribbon cable from
50-pin
connector
J51
on
the
motherboard
has two parallel connectors
mounted
on
the
compu-
ter base.
The
printer plugs into
and
obtains its power from
one
connector,
and
the
keyboard
from the other.
The ribbon cable from the
lOP card
in
the stack connects to the motherboard via 50-pin connector
J50. Another ribbon cable from this connector has two parallel connectors mounted
in
the base.
The printer plugs into
one
for
its
lOP bus, and the keyboard plugs into the other.
The
110
bus signals from connector
J50
are
prOVided
via traces to
J40
for presentation to the
110
backplane as described above.
1/0 Backplane
The
110
backplane plugs directly into the motherboard and has
14
connectors. It has several
functions as
follows:
• Provides power
and
signal connections from the motherboard to the:
a.
Display
b.
110
cards
c.
Mass storage controller cards
d.
Bootstrap loader card
e.
Other connections reserved for future use
• Translates between the lOP
and
110
cards
• Provides a connection for the
110
door interlock switch
The
backplane plugs into the
motherboard
via 96-pin receptacle
header
J12.
Most of the
motherboard
signals are routed to the display, the four
110
slots,
and
the two mass storage slots.
Display
Backplane connectors
PI
and
P2 provide
power
and
110
signals, respectively, to the display.
All
signals
come
from
thE~
motherboard
connector.
PI
and
P2 are both 50-pin ribbon headers.
110
Bus
Four 80-pin headers, P3 through P6, provide interconnection for up to four
110
cards and/or device
adapters. The backplane terminates some signal lines with resistor networks.
Other signals are
derived on the backplane with resistors
and
chips. A 14.7456
MHz
clock signal
is
produced
on
the
backplane.
Several types of
110
cards can be used
in
the computer. Refer to the documentation provided with
the card/adapter
for
more information.
Mass Storage Bus
Two 70-pin header connectors,
PIa
and
P11, provide the mass storage bus to the controller
card(s}. The bootstrap loader card plugs into
P11 if there
is
no Winchester Fixed
Disc
Drive
in
the
computer.
To Next Page
Loading...
Need help?
General
