Fluke 9132A, Service Manual

Page: 27 / 92

9132A Service
enables the select and chip enable on
pin 22
and
24
of the ZIF socket
(J5),
where the UUT ROM is plugged
in. When these two pins are enabled on
the
ZIF socket, data lines from the ROM in
the socket are placed
on
the data
lines to
J1
and
J2.
All pin signals from the UUT boot ROM
socket
are
connected directly to the
ZIF socket, except for pins 22
and 24. These
are
pins usually used for chip
enable or output enable, depending on the ROM
type
in
the ZIF socket.
The address lines from the UUT pass through one of the protection hybrids
(Al or A2) and a buffer (U3, U4, U5). The output of the buffer then drives
through a back-terminating resistor,
and then out J3
and J4 to the Pod and
the 9132A Main Board.
The ROM Module PAL
(U2)
determines whether any given
pin
on the UUT
ROM is
an output enable or chip
select, and
whether the polarity of the pin
is
active high or
low.
The PAL also inputs PROTPIN22, 24, 28,
and 29 from
Al
(protected signals from the UUT ROM). With these signals, the PAL
forms a ROM select output that makes all
the chip enables and output
enables active. This also determines the outputs for pins 22 and 24 of the
ZIF socket.
Other inputs
to
the PAL include RUNUUT, PWRFAIL, and PFUSESENSE.
The
RUNUUT
signal
tells the PAL
to
disable the ERAM data buffer
(U1)
and enable the ROM select outputs to the ZIF pins. The power fail line,
PWRFAIL,
disables the ROM Module
by
tri-stating all
the outputs.
The PWRFAIL line on the PAL
is
derived from a signal from the UUT cable
called RAWPWRFAIL. RAWPWRFAIL is connected to VCC through the
ROM plug adapter (e.g., pin 24 of J3 to pin 2 of J2
on
the 24-pin ROM plug
adapter). The VCC or power pin
on the
UUT enters the ROM Module at J2
pin
12,
goes through a resistor divider consisting of
RS and R3, and then
through the protection hybrid
Al. The signal coming out of
the protection
resistor is called PROTPWRFAIL. This signal goes through U3 and is
ed
PWRFAIL. From there the signal goes to
the
PAL and out I3 to the
When the fuse
sense
line becomes active, it performs
the
same function
as
PWRFAIL. (One side of the fuse is tied to
the
Pod ground. The other side
is
tied to
all
the grounds
on
the lines to the UUT and the ground from the
ZIF socket, which
is
also tied
to
+5V through
a
pull-up resistor. If this line
can be pulled high, the fuse
is
blown,
and
the fuse sense line goes
high.
The
fuse sense line is identical to UUT ground.)
Three lines on
J1
determine ROM type (ROMTYPEI, ROMTYPE2, and
ROMTYPE3).
These lines are connected
to pull-up resistors in
the ROM
Module and are either grounded or left open on
the ROM plug adapter.
See
the table on the ROM Module schematic for the decoding for ROM type.
ROM Plug Adapters
2-12.
The ROM plug adapter schematic diagrams are shown
in
Figure 5-6.
The various ROM plug adapters (connected
to J1
and J2 of the ROM
Module) adapt the end of
the micro ribbon cables
to
the correct pins on the