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10-2.
CIRCUIT DESCRIPTION
(1)
The
signalflow
(a) Transmission
(b)
(c)
@The
image data of the original conveyed through
the reading mechanism is read by the Contact
Image Sensor (CIS) and this data is transfered to
Ml PCB.
@In the Ml PCB, the data is amplified, rectified and
turned into two values (black and white) or halftone
signal through the image Processing, then this data
is written into one line memory (SRAM).
@The CPU reads out and encodes the data written in
line memory, then stores the data into the FIFO
(SRAM). At the same time, the CPU transfers one
byte data in
the FIFO
to the MODEM
with an
interruption signal requested
by the M@DEM.
@Through
repetition of above operations,
the image
data
for
each line is encoded,
modulated
through
the MODEM,
and transmitted over the line through
the
NCU.
Reception
@The
signals received
from the line enter the
MODEM through the NCU.
@In the same manner as in transmission, the coded
data which is demodulated
by the MODEM
is
stored into the FIFO as one byte data with an
interruption signal requested by the MODEM.
o The CPU reads out and decodes each one bit of the
data from the FIFO, and outputs to the thermal head
when each one bit portion of decoded data is
aligned as one line data.
@)Through repetition of above operation, the received
data is printed to the recording paper.
COPY
@In the same manner as image reading in transmis-
sion, the image data read by the CIS is turned into
two values (black and white) or halftone signal, then
it is stored into one line memory (SRAhl).
@The
CPU reads out the data of one line memory,
and outputs the data of each line to the thermal
head.
-43—
Power Supply Circuit (M5)
Switching
regulator
type
power supply circuit outputs
+24V,
.112V and
-1-5V.
*I 2V and
-t5V
are
for the Main
Board
(Ml :CPt_f), 124V,
is
for
the
NCU
circuit,
pulse
motors,
LED
array
and
thermal
Head
as HV.
HV is controlled
by the signal (HVON) from
CPU.
(A) Noise Filter
Line filter circuit
suppress
the internal noise flowing
out and external
noise flowing
in.
(L501, L502,
C501 , C503 -C505)
(B) Rectification
and Smoothing
(Primary)
Bridge rectifier
diode and smoothing
capacitor
make
DC High voltage,
and supplied
for switching
circuit.
(D501 , C509)
(C) Switching
Circuit
Transformer
transfers
the primary energy to second-
ary circuit
by switching
oscillation
of transistor,
(T501, Q501)
(D) Switching
controi
circuit
Switching
cont[ol
IC works as follows.
Keep the switching
frequency
constant.
Stabilize
the output
124V condition.
.
Protect
from abnormal
over load condition.
(IC501 )
(E) Rectification
and
Smoothing
(Secondary)
AC
low
voltage
generated
in secondary
windings
of
transformer
are
rectified
and
smoothed
by the
diode:
and
the
capacitors.
E24V
Line
""
(D504,
C517)
-I 5V
Line
~"~~.. (D507,
C525)
i 12V
Line ~ ""."' (D508, C528)
–12V
Line . ... . (D509, C529)
(F) Voltage
Regulators
I-5V
is regulated
by 3 pins type voltage
regulators.
(IC502)
(G) Comparator
Comparator
circuit
feeds back the fluctuation
of the
output
124V
to the switching control circuit through
Photo-Isolator.
(Q502, ZD503,
P501)
(H) Semiconductor
Switch
Circuit
+24V,
named HV is supplied for the thermal head by
on/off
operation
of FET controlled
HVON signal from
CPU.
(Q503 - Q505)
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