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All
and
more
about Sharp
PC-1500
at
http://www.PC-1500.info
Refering to
the
block
diagram,
the
CE-150
is
the printer
(DGP! 301)
and the
CMT (cassette tape
recorder
interface) which
consists
o
f
three
blocks, the
CMT interface,
printer interface
and
power
supply
circuit.
• CMT interface
"!he
CMT interface is the
circuit
that handles
data transfer
betwe.en
the
PC· I
500 and
the
CMT and
consists
of
a
simple
driver
circuit (voltage level conversion
circuit).
In
addition, there is
the
CMT
on/off remote
controlling circuit
which is under
the program
control
of
the PC-I 500 and performs switching operation via the
1/0
port
usiJig the relay
circuit.
•
Pr
inter
interface
The
printer intefoee
consists
of character generator
ROM
(LH5367-01),l/0 port
(
LH580J),
motor
drive
circuit,
print
solenoid drive circuit, and
the
pen color
detect
input
signal
circuit.
•
Power
supply
block
A
simple
power
stabilization
circuit is
provided
to
take
care
of
recharge
to
the
built-in
NiCd
batteries from
the
AC
Adaptor.
3. CIRCUIT DESCRIPTION
3· 1.
CMT
Interface
circuit
diagram
e
The signal
CMT
OUT is sent from
the
PC-1
500 to write data on the cassette
tape
and
the capacitor
coupled
interface
circuit
is
provided to shift
the
voltage level
before
supplying
the MIC jack. The
read signal is the
input
from the £ARPHONE jack and passed
through
the
capacitor and
two stages
of gates
to
perform voltage
level
shift and waveform
shaping
and delivered
to
the
PC-
I
500 as
the
CM!T IN signal.
With
respect to
the CMT
IN
signal
,
the gate
input
to
the
first
stage
of the gate is forced to a low
level by
means of
the
PAO
signal
as there
is a
possibility
of supplying
noise
to
the
EARPHONE
jack
as
input
data to
the
PC·
I
500, except during
the
data read
mode.
Do
not
sale
this PDF
!! !
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