Force
FXTM-C
Service
Manual
Control
Board
Feedback
Microcontroller
Memory
APS0412
(U6)
provides
program
memory
(64K x 8
external
EPROM)
and
data
memory
(2K x 8
external
static RAM) for
the
feedback
microcontroller.
Additional
data
memory
is
available
from
these
sources:
• 256K x 8
microcontroller
internal
RAM
• 4K x 8
external
static
RAM
(U4)
shared
with
the
main
microcontroller.
Shared
RAM
The
4K
x 8
external
shared
static
RAM
is
provided
by
an
lOT
71342SA
device
(U4)
with
semaphore
flags.
The
shared
RAM
311o'ws
the
main
microcontroller
(U5)
and
the
feedback
microcontroller
(Ull)
to
share
common
variables.
It
ttmctions
as
a
communications
interface
beh,veen
the
main
and
feedback
microcontrollers.
It
also
provides
additional
general
purpose
RAM
to
these
microcontrollers.
110
Expansion
Three
devices
provide
I/O
expansion
capabilities:
•
One
PS0412
programmable
peripheral
(U6)
•
One
PSD413
programmable
peripheral
(U3)
•
One
82CSS
expansion
port
(U2).
Each
programmable
peripheral
device
incorporates
forty
individually
programmable
I/O
pins
divided
into
five 8-bit
ports.
Twenty-four
of
the
general
I/O
pins
can
alternatively
be
used
as
I/O
for
two
PLDs,
featuring
a total
of
59
inputs,
126
product
terms,
and
24 macrocells.
Each
device
also
contains
EPROM
(64K x 8 for
the
1'50412; 128K x 8 for
the
PS0413),
2K x 8
of
static
RAM,
and
a
power
management
unit
for
battery
backup.
The
I/O
expansion
capabilities
of
both
devices
are
configured
as
outputs
for
relay
controt
lamp
control,
keyboard
scmming,
and
chip
selects.
The
expan.sion
port
82eSS
(U2) is a
generic
I/O
expander
that
incorporates
twenty-four
I/O
pins
divided
into
three
8-bit
ports.
It
is
configured
as
all
inputs.
It
reads
the
keyboard,
activation
signals,
accessory
svvitches,
and
system
status
flags.
Keyboard
Interface
and
Activation
Inputs
The
keyboard
interface
is
a
simple
row
and
col
umn
matrix
between
three
bank
select
output
lines (BANKO-BANK2)
on
port
A
of
the
PSD413 (U3)
used
by
the
main
microcontroller
and
eight
keyboard
(KBO _,DO-KBD
_07)
input
lines
on
port
A
of
the
expansion
port
82CSS (U2).
Port
B
of
the
expansion
port
82C55
reads
activation
inputs
from
the
IsoBloc
decoding
circuits
on
the
Power
Supply
/RF
board.
4-7
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