Reset Circuit; Sensor Circuit; Figure 2-18. Reset Circuit Block Diagram; Figure 2-19. Sensor Circuit Block Diagram - Epson STYLUS PRO XL 4004677 Service Manual

Operating Principles
2.3.2.1 Reset Circuits
The C162 MAIN Board contains 2 reset circuits: the +5 V monitor reset circuit and the +35 V
monitor reset circuit. The +5 V monitor reset circuit monitors the voltage level of the +5 V line,
using reset IC PST592D (IC12), and outputs a reset signal to the E05A96 gate array (IC2) when the
voltage level drops below +4.2 V. The +35 V monitor reset circuit monitors the voltage level of the
+35 V line, using reset IC M51955B (IC8), and outputs a reset signal to the CPU. The reset signal is
generated when the voltage level drops below +28 V, and this causes a non-maskable interrupt
(NMI).
+35 V
+5 V
2.3.2.2 Sensor Circuits
The following sensor circuits enable the C162 MAIN Board to monitor printer mechanism status:
HP sensor The photocoupler-type home position (HP) sensor is attached to the surface of the
printer mechanism to detect the carriage home position. A LOW level from the
signal indicates that the carriage is in home position.
PE sensor The mechanical switch paper end (PE) sensor is built into the printer mechanism to
determine whether there is paper in the printer or not. A LOW level from the signal
indicates that no paper is loaded.
BCO sensor, The cartridge out (CO) sensor is micro switch attached to the bottom of each ink
CCO sensor cartridge holder in the carriage unit. When the ink cartridge is installed, these
switches are pressed and a LOW level from the signal indicates that the ink
cartridge is installed into the ink cartridge holder.
Thermistor A thermistor is attached to the color printhead driver board to monitor its
temperature by thermister's resistance value (at 25 C approx. 10k ). The CPU
changes the printhead drive signal's pulse width (charge pulse width) based on the
temperature level.
(CN8)
(CN9)

Figure 2-19. Sensor Circuit Block Diagram

2-16
+5 V
M5 195 5B
(IC8)
6
PST5 92D
(IC13)
1 1 3 5

Figure 2-18. Reset Circuit Block Diagram

+ 5 V
CPU (IC1 )
8 7
1
P E
A N 1
2
8 6
1
A N 0
H P
2
3
CPU (IC1)
NMI
7 2
P 6 2
6 8
RES
7 1
E05A96 (IC2)
RESET
PA8
5 5
+5 V
1 0
89
A N 3
T H
9
8
91
A N5
C C O
9
8
90
AN4
B C O
Stylus Pro XL
RST
Typ e B
(CN12)
(CN11)
REV.-A