6.
Cassette
SAVE
Load
Circuit
Cassette
SAVE
circuit
convert
the
data
signal
from
MPU
to
serial
signals
by
ACIA
(Asynchronous
Communications
Interface
Adaptor).
This
signal
is
converted
to
FSK
(Frequency
Shift
Keying)
signals
by
the
1.2
KHZ
and
2.4
KHZ
signals
which
are
generated
by
dividing
E
signal,
then
outputted
to
SAVE
signal
of
the
Cassette
Recorder.
Cassette
Load
Circuit
convert
the
played
signals
from
Analogue
signal
to
digital
signal,
by
PLL
Circuit,
also
convert
from
serial
signal
to
parallel
signal
by
ACIA
then
outputted
to
MPU
data
bus.
7.
RS232C
Interface
Circuit
In
RS232C
Interface
Circuit,
l6.l28
MHZ
clock
divider
generates
the
receive/send
baud
rate,
and
Sends
this
Signal
to
ACIA
as
recieve/send
clock.
In
case
or
sending,
according
to
the
set
baud
rate,
the
data
signals
from
MPU
is
sent
by
converting
to
serial
signals,
and
v i S @ V @ f S @ »
in
case
of
the
receiving,
recieved
serial
signals
are
converted
by
ACIA
and
outputted
to
data
bus
of
MPU.
8.
Light
Pen
Interface
In
the
Light
Pen
Interface
Block,
when
light
pen
is
ON,
this
is
detected
by
IRQ
interrupt
then
inputsthe
pen
location
signal
(LP
STB)
to
CRTC
(CRT
Controller).
9.
Acoustic
Output
Circuit
The
acoustic
output
circuit
uses
the
class
E
push/pull
method,
and
is
used
for
the
keyboard
input
Click
sound
and
beep.
Содержание MB-6890
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