Electrical Circuit; Transmission Circuit - Epson GT-1200 Service Manual

ADF

2.1.2 Electrical Circuit

This ADF (R-4C1070).is equipped with only one control board. This
section describes the functions of the board.

2.1.2.1 Transmission Circuit

The transmission circuit manages parallel and serial signal transmission
between the ADF and the scanner. The protocol used between them is
original.
q Serial transmission
IC11 is the transceiver used for the serial transmission. It receives
output signal from the CPU and separates them according to the
signal types; reversed or non-reversed, then it outputs the signals to
the scanner from DO1. 2 signals (RI1 and RI2) sent from the scanner
are combined into 1 signal and output from the RO1.
q Parallel transmission
Signals sent from the CPU is output at the open collector via IC1 and
IC3. Signals from the scanner are transferred to the CPU via the pull-
up resistor.
Rev. A
CN6
1 TXD
DA2
2 *TXD
R62
3
RXD
4.7K
4
*RXD R81
DA1
220
5
DTR
R63
6 DSR
4.7K
7 GND
8
OP1
GND
9
OP2
GND
Q3
+5V
R36
GND
1.0K
R64
4.7K
Figure 2-42. Transmission Circuit Block Diagram
Operating Principles
+5V
IC11
1
3
79
RO1
*RI1
2
RI1
80
DI1
14
DO1
4
13
*DO1
*RE
6
*RI2
15 21
DE
7
RI2
R35
5
10
RO2
1K
DO2
11
*DO2
9
DI2
GND
GND
B
Y DTR
A
IC1
DSR
IC12
RXD
TXD
CPU
TXEN
2-12