AR-FN1 (serv.man10). ARFN1 Service Manual-Description of Circuits - Sharp Copying Equipment Service Manual (repair manual). Page 8

In the communication buffer circuit, the transmission signal (F-TXD)
and communication permit signal (F-DTR) from the copier is received
by the transistor array TD62504 (IC14), while the reception signal
(F-RXD) and communication request signal (F-DSR) transmitted from
the finisher to the copier is output from the IC14.

The reset signal from the copier is also received by the IC14 and
input to the CPU’s reset terminal (active at L). In addition, the rever-
sion signal is input to the expansion I/O reset terminal (active at H).
For each signal, a protective diode is inserted between 

+

5V and

GND.

Signal

name

Description

Logic (connector level)

F-TXD

Signal line from copier to finisher

Start bit detection at H
Usual (marking state) at L

F-RXD

Signal line from finisher to copier

Start bit detection at L

Usual (marking state) at L

F-DTR

Status display signal line for the signal showing communication permit
from finisher to copier

Communication from finisher to copier is inhibited at H
Communication from finisher to copier is permitted at L

F-DSR

Status display signal line for the signal showing communication request
from finisher to copier

No communication request from finisher to copier at H
Communication request from finisher to copier at L

F-RES

Hard rest signal from copier

Reset at H
Reset is released at L

CPU

(IC02)

I/O

(IC03)

RXD0/P92

TXD0/P90

P95

P94

RES

RESET

TD62504F

TD62504F

TD62504F

TD62504F

TD62504F

TD62504F

TD62504F

IC14

IC14

IC14

IC14

IC14

IC14

+5V

+5V

+5V

+5V

+5V

+5V

+5V

+5V

+5V

+5V

+5V

BR14-2
4.7K

BR14-6
4.7K

BR12-2
4.7K

R199

1K

R139
1K

3

14

7

10

BR14-7
4.7K

BR14-5
4.7K

BR12-6

4.7K

BR12-3
4.7K

BR14-3

4.7K

15

2

12

5

11

6

BR14-4

4.7K

13

4

IC14

16

1

+5V

BR12-5

4.7K

+5V

1SS133x5

0.1U

1SS133x5

RES/

RES

14

F-TXD

F-RXD

12

17

F-DTR

F-DSR

16

63

33

F-TXD

F-RXD

F-DTR

F-DSR

F-RES

C131
0.1U

D14 D18 D15 D17 D16

D9 D13 D10 D12 D11 C171

from Copier

The signal from each sensor is 10 kohm pull-up resistance, noise-re-
moving 1000 pF capacitor, 10 kohm protective resistance, CPU, and
expansion I/O input port. 

The sensor signal for transfer system is input to the schmitt trigger
input port because the sensor input circuit is not provided with rectifier
circuit.

+5V

+5V

1000PF

P**

10K

Ω

(IC02)

AMP

*1

*1:Rated Voltage Sircuit

CPU

+5V

+5V

1000PF

PA or PB

(IC03)

*2

I/O

10K

Ω

10K

Ω

10K

Ω

240

Ω

HP sensor

Transfer system sensor

*2 Schumit trigger input port

9 – 6