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for line buffering, and out
inverting
(U3) is an
reinverted
in
prevent pulse width distortion.
helps
to
Every other line on the J2 connector
"mostly" AC ground.
These AC circuits ensure
resistor.
none of the leads can be directly shorted to another
One DC ground exists on J2 called fuse
the DC return path for channel
2
ne.
Another fuse and DC return path (FUSE1-GND)are available for the UUT
reset overdrive line at hole
The two fuse circuits are ORed together
(FUSESENSE)
and C10)
C9,
overdrive pulses occur, the AC capacitors limit the voltage to zero volts for
a short time
cause too much voltage drop). The diodes
protect the back-to-back capacitors.
The overdrive circuits (overdrive reset
driven either high or
exclusive OR gates
shifting network of diodes,
(either high or low).
high is connected to +12V through a current-limiting resistor
Overdrive low
The
capacitors in the overdrive circuit
small
speed-up purposes.
reverse voltage protection for transistors Q1,
CR6, CR7,
and CR14
overdrive output protection circuit.
the
overdrive high and overdrive low drive transistors prevent the transistors
from turning
on at
Modules
ROM
(24-, 28-,
28-, and 32-pin ROM Modules use
24-,
loaded with parts that determine the desired ROM component
ROM Module schematic diagram (Figure
J3 and J4 connect to the ribbon cables
ribbon cables to the ROM Module header assembly. The data lines from the
9132A Main Board
and out to the data lines
(A1)
ROM select (ROMSEL-) from
Ul.
enable
on
switching for the UUT ROM occurs, the PAL disables ROM select, and
Pod. The buffer
J1
to
the
The
buffer.
the Pod. The double inversion reduces propagation delay
Each AC coupled line contains a 1-megobm bleed
3 (J2
Reset overdrive (OVDRV1)
E2.
The large bypass capacitors across the fuses
line.
used for AC coupling when overdriving.
are
fuses alone have about
(the
The overdrive highs
low.
U1B, UIC,
(U1A,
then turn
and
The transistors are
-5V through a current-limiting resistor
connected
is
to
The diodes
CR1,
compensate for
the same
time.
and
Assemblies)
32-Pin
through a buffer
go
the UUT microprocessor.
on
the
When the Pod is in RUNUUT mode or
the status control lines
on
that pass through
signals
a ground line or,
is
when
flying lead
the
that,
lead.
2
ground (FUSE2-GND). This line
pin
24), the Sync
is at
create the fuse sense
to
ohms resistance, which would
25
CR11, CR12,
(CR10,
overdrive channel
and
lows
and
are
and
U1D),
output to a voltage-
are
appropriate transistor
the
on
voltage followers. Overdrive
all
(C1, C2, C3, and
CR2, CR3,
and
Q3,
and
Q2,
voltage drop from
the
CR16 between the
CR15
and
same bare circuit board, but
the
for details.
5-5)
and J2 connect to the
the Pod.
J1
to
a protection hybrid network
(U1) and
ROM Module
PAL
9132A Service
buffer
this
are
and
in
most cases, a
is
set
used,
Module overdrive
hole
E3.
(C7, C8,
When short
and
CR13)
be
3)
can
a set of
gated
by
(R10).
(R11).
C4) are for
CR4 are used
as
Q4. Diodes
CRS,
level shift of
the
2-11.
are
See the
size.
controls
(U2)
the
when
dynamic
2-13
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