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17

ASIC

IC10

32.768KHz

24MHz

+5V

Thermal Head

CIS

RESET

IC13

DRAM

4Mbit

IC17

Motor

Motor Driver 

IC401

PRINTER

CONTROL

A/D

RTC

CPU

256Kbit

ROM

64Kbit

SRAM

MOTOR

I/F

TX

RX

OP-PANEL

I/F

IMAGE

PROCESSING

OSC

32.256MHz

+6V

+24V

Power Supply Board

KEY MATRIX

DSET

GATE ARRAY

IC301

LCD PANEL 

2Line

Operation Panel Board

Relay

T101

Digital Board

Analog Board

+24V

+6V

MODEM

BOA

9600bps

IC3

SERIAL

TONE

AUTO ANSWER

+2.5V

SP AMP IC2

DTOP

Flash

Memory

4Mbit

IC16

RF

IC28

REG

REG

+6V

+5V

ANT

10.368MHz

Dual

Flash

Memory

16Mbit

IC23

EEPROM

128K (*1)

IC22

(*1)

KX-FC253UA-T......32K

KX-FC258RU-T......128K

Charger

REG

+4V

+4V

I/F Board

+4V

+6V

+4V

+24V

Motor Position

AC

+3.3V

REG

+4V

+3.3V

FET Q401

Film End

Tr

MIC

-5V

REG

+5V

Speaker

T102

PTOP

REED

COVER OPEN

Handset

BBIC

IC4

Hook

+5

V

+24V

+5V

-5V

Sensor Board

Sensor Board

Hook SW Board

KX-FC253UA-T / KX-FC258RU-T : GENERAL BLOCK DIAGRAM

EXT.

LINE

DECT Handset

+

-

IC7

IC8

IC29

Sensor Board

18

This custom IC is used for the general FAX operations.

1. CPU:

This model uses a Z80 equivalent to the CPU operating
at 12 MHz. Most of the peripheral functions are performed
by custom-designed LSIs. Therefore, the CPU only works
for processing the results.

2. RTC:

Real Time Clock

3. DECODER:

Decodes the address.

4. ROM/RAM I/F:

Controls the SELECT signal of ROM or RAM and the
bank switching.

5. CIS I/F:

Controls the document reading.

6. IMAGE DATA RAM:

This memory is programmed into the ASIC and uses 8
KB for the image processing. 

7. THERMAL HEAD I/F:

Transmits the recorded data to the thermal head.

8. MOTOR I/F:

Controls the transmission motor which feeds the docu-
ment.
Controls the receiving motor which feeds the recording
paper.

9. OPERATION PANEL I/F:

Serial interface with Operation Panel.

10. I/O PORT:

I/O Port Interface.

This memory is incorporated into the ASIC (IC10) and used for the image processing.
Fig. A shows the memory map of the Image Data RAM.

This 512KB ROM (FLASH MEMORY) carries a common area of 32KB and bank areas which each have 8KB (BK4~BK63). The
addresses from 0000H to 7FFFH are for the common area and from 8000H to 9FFFH are for the bank areas.

The DRAM serves as CPU and receives memory.
The address is F200H~F3FFH (DRAM access window 1) and F600H~F7FFH (DRAM access window 2).

19

The output signal (reset) from pin 2 of the voltage detect IC (IC10) is input to the ASIC (IC10) 114 pin.

1. During a momentary power interruption, a positive reset pulse of 60 msec is generated and the system is reset  completely.

2. The watch dog timer, built-in the ASIC (IC10), is initialized by the CPU about every 1.5 ms.

When a watch dog error occurs, pin 115 of the ASIC (IC10) becomes low level.
The terminal of the 'WDERR' signal is connected to the reset line, so the 'WDERR' signal works as the reset signal.

20

1. Function 

 The thermistor changes the resistor according to the temperature and uses the thermistor's characteristics. The output of pin
139 of IC10 becomes a low level. Then when it becomes a high level, it triggers point A In point C, according to the voltage
output time, the thermal head's temperature is detected.
 After the thermal head temperature is converted to voltage in B, it is then changed to digital data in the A/D converter inside
IC10. The CPU decides the strobe width of the thermal head according to this value. Therefore, this circuit can keep the ther-
mal head at an even temperature in order to stabilize the printing density and prevent the head from being overheated.