Samsung MSYS 5200, Service Manual

Page: 46 / 210

5-30 Samsung Electronics
Circuit Description
5-6 Engine Controller
5-6-1 Power On Reset
The reset circuit initializes the CPU(U3) at power on
and prevents unstable operation due to power
fluctuations. It consists of LM393(U5) - voltage
comparator-, and RC for reset timing.When a DC
3.8V or higher are applied to LM393’s pin #3, the ‘
RESET’ signal goes ‘HIGH’ and the CPU begins the
initialization procedure, ‘RESET’ is active for
approximately 122ms.
5-6-2 CPU(+5V)
The used CPU is a 8bit microprocessor, SAMSUNG
KS88C4316(U3). This is operated at 6.944MHz and
controls all ICs. The shape is a 64pin DIP type.
5-6-3 EPROM (+5V)
The EPROM, 27C256(U2), has the storage capability
of 256KBits and the access time is 150ns. The
EPROM stores the program data that controls the
Engine part.
5-6-4 Address Latch
There contain Address and Data in CPU
port[1.7:1.0] signals. This signals are applied to
LS574(U4) and Addresses synchronize with
“AS”(Address Strobe) and output to EPROM(U2).
5-6-5 Extended Output Ports
HC259(U12) is composed of 3-to-8 Decoder and
Output Latch. Address x8000 to x8007 are mapped
Output Port, the D0 value is latched ports. This
outputs control the clutch, LSU, HVPS.
5-6-6 NVRAM Control
The NVRAM(U1) stores “Used Sheet Count” for
SET and Developer unit. To control it, it is selected
by “CS”, and “DI”/”DO” synchronizes with “SK”
clock writes in/reads out the serial data to/from the
N V R A M .
5-6-7 Motor D24V)
The Motor Driver, SLA7029M(U207), is used to
drive the Main Stepping Motor. A n
SLA7029M(U207) receives Motor Drive Enable and
two phase signals from the CPU. It then generates a
constant-current unipolar pulsed signal for Motor
driving, applied to the Motor through R5(1
Ω
, 5%,
3W) and R6(1
Ω
, 5%, 3W).
5-6-8 Solenoid 24V)
The Solenoid controls the paper Pick-up Clutch. The
Solenoid receives control signal from U12 Q0.
KSC1008-Y(Q4) is the driving transistor, and
1N4003(D1) protects KSC1008-Y(Q4) from the noise
pulse generated by deenergizing the Solenoid
5-6-9 Fuser C24V, AC Power)
The Fuser Temperature Control circuit reads the
Heat Roller’s Thermistor voltage at CPU port 5.0,
and turns the Fuser unit on and off via CPU port 6.4
and KSC1008 (Q3). If CPU port 6.4 or LM393(U5)
pin #7 are ‘LOW’, KSC1008 is off and the Fuser
Lamp is off. LM393’s pin #5 is proportional to fixing
unit’s temperature. LM393 pin #6 is the
‘OVERHEAT’ signal. If LM393 pin #5 is less than its
pin #6, its pin #7 output is ‘LOW’, keeping the
fixing unit off. The ‘Fuser on’ signal of Q3 turns the
Triac through the Photo LED on inside the Photo
Coupler(PC251). And PC151 trigger input signal
supplies into the Triac Thyristor(Q201), then the
Fuser’s Heat Lamp turns on.