Epson LQ-2550 Technical Manual page 102

2.3.3 Control Panel Interface Circuit
Figure 2-51 shows the control panel interface circuit.
This circuit is mainly divided into the following three blocks:
LED drive section
Switch status read section
LCD control/drive section
Descriptions of the above sections will now be given.
Refer to Figure A-55 for the detailed circuits on the ROPNL board.
D3
2A
D2 3A
4A
DO 5A
AO
1A
W E
6A
+5
t
PB 1
R75
R66
PC3
C40
RDY of ~fl
M 5 4 6 10P( 11 B)
3Y
4Y
5Y
6Y —
LS365
+5
777
LOAD '
DTO Q
,
Figure 2-51. Control Panel Interface Circuit
CN8
LCD SELL
(20
columns)
CONTROLLER
5
' P O W E R
LED
1
SWITCH STATUS
READING CIRCUIT
ONLINE SWITCH
STATUS
2-55
+ 5
LCD
RESET
CIRCUIT
+5
P O R T -
EXPANDER
DRIVER
Ic
DRIVER
v
PANEL
LED ( xl 4)
LED (
X