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2. Printed Data Interface

Printed data which is memorized in Page Memory is transferred from IPC to Laser Diode in LSU. The transfer trigger is
HSYNC (1 ms / line) which is generated from Laser Beam Detection Sensor (Horizontal Synchronized Sensor) of LSU.

nSBSY

(Control        Printer)

nCBSY

(Control        Printer)

Command data

Status data

Command data sampling timing

(Printer side)

Status data sampling timing

(Controller side)

Controller transmits clock

Controller transmits clock

52 

µ

S

52 

µ

S

nSTA

(Control        Printer)

nCMD

(Control        Printer)

nSCLK

(Control        Printer)

nCBSY

Command Data Busy

nSBSY

Status Data Busy

nCMD

Command Data

nSTA

Status Data

nSCLK

Controller Clock

26

This circuit consists of four-chips modem IC (Modem CPU, Analog Modem, FROM, SRAM) and peripheral circuitry.

1. Modem CPU : Digital Signal Processor

Digital Modulation and Demodulation, DTMF generation, Output level control 
This modem conforms to ITU-T (former CCITT), V.34, V.29, V.27ter, V.21 channel 2 (FSK) and T.4.

2. FROM : Modem Program Software
3. Analog Modem : Analog to Digital & Digital to Analog converter
4. SRAM : Data buffer
5. Analog Master : Op-Amp for TX/RX filter and analog SW for Monitor volume

1. TX Signal

Modem CPU modulates coded data and Analog Modem converts from digital to analog fax signal. And it sends from TXOUT
of Analog Modem to PSTN line through Analog Master and HYBSR Amp and LCU/LCE PCB.

2. RX Signal

Analog Modem (RXIN) receives analog fax signal through PSTN, LCU/LCE PCB, HYBSR signal line, RX Amp. And it 
converts to digital and transfers to Modem CPU.

Alarm sound, key sound of panel and line monitor sound are generated by speaker through Speaker Driver Circuit (IC100). 
The volume and ON/OFF SW is controlled by Analog Master.
Note:

Modem Peripheral Circuit can be always checked by using TEST MODE 5 (1650Hz output)

HYSIG

Rxsig

Txsig

Hybrid

AGC

Gain Amp

Ain(M)

Aout(M)

Aout(V)

Analog Master

LPF 

LPF 

HYBSR

SW

SW

SW

Speaker

Panel

Amp

DPS

Analog Modem

Not used

VOL1 - 3

SPON

MON5W

BZCK

Modem

CPU

ROM

SRAM

24.576 MHz

I/O Bus

27

LBP is controlled by LBP CPU and peripheral driver on LPC PCB. The LBP CPU used in this printer is 8-bit one chip CPU. 
This CPU controls the laser printer mechanism, fuser lamp temperature, laser unit, etc.

This circuit consists with IC701 (PST575) and peripheral circuit. This circuit always watches 5 V. Output of this circuit (nRST ) to LBP
CPU is set to low if 5V falls below setting level (3.9V). When the 5V is risen back above voltage, the reset signal is canceled after a
delay of approximately 20 ms. After cancel, software is started by CPU after 26 ms.

1. Printer Motor Driver Circuit

The Motor is DC brush motor. The rotate start signal (pMMON) is outputted by IC51, Pin6. When the speed of motor becomes
constant, the Ready signal (nMMRDY) will output by DC Motor, The Printer Motor is powered by +24VDC supply, When the
interlocks are open, the +24 VDC supply is cut off and the Printer Motor will stop rotating.

2. Sensor Circuit

In port of LBP CPU detects Paper Timing, Paper Eject, Cassette Sensor.

+5V

R708

R401

R709

R402

35

C713

GND

VCC

PST575E

 IC701

GND

GND

1

1

2

2

3

3

4

CNP69, 13

13

pPRST

CD

OUT

Q101

IC51
CPU

C402

1

2

CNP59

Q514

Paper Eject

Sensor

Paper Timing

Sensor

Cassette Sensor

No Document : 5V

No Document : 5V

No Cassette : 5V

DC

Motor

+24 VM

Motor

Driver

nMMRDY

pMMON

nMMP2

nMMP3

CPU

IC51

28

The fuser temperature is controlled by IC51 on the LPC PCB. LBP CPU has A/D (Analog / Digital) converter circuit and detects th e
temperature by using thermistor. Due to the temperature, CPU controls Fuser Lamp through nSSRA signal, Q601, Q602 on FCB
PCB and photo-capler SW (PC301) on Low Voltage Power Supply (LVPS). IC55 is used as an abnormal temperature detection 
circuit. It compares thermistor output voltage with input of pins 3 (4V). When the thermistor output voltage level (VTH) becomes
higher than 4V (abnormal temperature), IC55 becomes pin1 to Low and deactivates Q6O2. Abnormally low & high temperatures
and opened Thermistor are detected by IC51 (CPU) programming.

GND

Q602

3

GND

Q601

3

+5v

R616

2

2

+5v

R615

R613

2

IC55

4

1

3

GND

GND

C602

R614

GND

R612

+5v

+24V

GND

TP201

PC301

1

2

6

4

+24v

R201

+5v

Thermistor

LVPS

nSSRA

nSSRA

8

1

1

47

LPC PCB

6

7

CN56

9

CN67

9

CN33

Fuser Temperature Control Circuit Diagram

(ANI0)

IC51

CPU