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10-2. CIRCUIT DESCRIPTION
(1) The signal flow
(a) Transmission
@ 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
M1 PCB.
@ In the M1 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 MODEM.
@ 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.
(b) 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.
@ 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.
(c) 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 (SRAM).
@ The CPU reads out the data of one line memory,
and outputs the data of each line to the thermal
head.
Power Supply Circuit (M5)
Switching
regulator
type power
supply
circuit outputs
+24V,
H2V
and
+V.
+12V and
+5V are for the Main Board (M1:CPU),
+24V
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
voitage,
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
control
circuit
Switching
control
IC works
as _ follows.
® Keep
the switching
frequency
constant.
® Stabilize
the output
+24V
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 diodes
and
the
capacitors.
+24V
Line --:* (D504, C517)
+ 5V Line --*: (D507, C525)
412V
Line ---- (D508, C528)
—12V
Line ----- (D509, C529)
(F) Voltage
Regulators
45V
is regulated
by 3 pins type
voltage
regulators.
(IC502)
(G) Comparator
Comparator
circuit
feeds
back
the fluctuation
of the
output
+24V
to the switching
control
circuit through
Photo-lsolator.
(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)
AOS
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