Reserved Bus; Bootstrap Loader Card Block Diagram - HP 9020 Service Manual

Theory of Operation
2-53
16-BIT
1
8K BYTES
LOADER
I - -
COUNTER
,
ROM
CONTROL
~
LOGIC
1
f
.....
~
I
,
STS/FLG ID
....
~
~ l
J
BUFFER
I J
BUFFER
I I
BUFFER
I
I I I
J I
f
lOP BUS
f
- - - - - - - - - -
Figure 2-26. Bootstrap Loader Card Block Diagram
Reserved Bus
Connectors P7 through P9 are 60-pin headers which provide three plug-in slots. Power and signal
lines are provided at the connectors. P13 is a 50-pin ribbon cable connector. All four connectors are
reserved for future use.
I/O Door Interlock
A switch mounted on an
110
card gUide is connected by a cable to P14, a 2-pin plug on the
110
backplane. When the
110
door is opened, a signal is sent through P14 to the motherboard. The
motherboard passes the signal to the power supply which then shuts down power to the computer.