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Circuit Description
5-6 Engine Controller
5-6-1 Power On Reset
The re s e t c i rcuit initializes the CPU(U3) at power on
and prevents unstable operation
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
i n i t i a l i z a t i o n p rocedure , ' R E S E T ' i s a c t i v e f o r
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 store s t h e p rogram data that contro l s t h e
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"(Addre s s S t robe) 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.
5-30
due to power
5-6-6 NVRAM Control
The NVRAM(U1) stores "Used Sheet Count" for
SET and Developer unit. To contro l i t , i t i s s e l e c t e d
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 Driving(+24V)
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(1Ω, 5 % ,
3W) and R6(1Ω, 5%, 3W).
5-6-8 Solenoid Clutch(+24V)
The Solenoid controls the paper Pick-up Clutch. The
Solenoid receives contro l s i g n a l f rom U12 Q0.
KSC1008-Y(Q4) is the driving transistor, a n d
1N4003(D1) protects KSC1008-Y(Q4) from the noise
pulse generated by deenergizing the Solenoid
5-6-9 Fuser Control(+24V, AC Power)
The Fuser Temperature Contro l c i rc u i t reads the
Heat Roller's Thermistor voltage at
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
f i x i n g u n i t o ff. The 'Fuser on' signal of Q3 turns the
Tr i a c t h rough 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.
CPU port 5.0,
Samsung Electronics
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