Epson Stylus Color 760, Service Manual

Page: 46 / 172

EPSON Stylus COLOR 760 Revision C
Operating Principles Electrical Circuit Operating Principles 46
2.2.2.2 Reset Circuit
Reset circuits are attached on the C298MAIN board to monitor the two
voltages: +5V for the logic line and +42V for the drive line. When each circuit
detects abnormality on the corresponding line, it outputs a reset signal to reset
CPU and ASIC. This function is necessary to prevent the printer from operating
abnormally. IC5 RTC-9820SA, a reset circuit IC, is attached directly on the
main board. This IC monitors both the +5V and +45 lines but can reset them
independently. See Figure 2-19 for the block diagram for the reset circuits.
o
+5V line reset circuit
The VDD port of the IC5 reset IC monitors the +5V line. When the IC
detects an abnormal voltage level (4.3 V or lower), it outputs a reset signal
from the RST port to CPU and ASIC.
o
+42V line reset circuit
The VIN port of the IC5 reset IC monitors the +45V line. When the IC
detects an abnormal voltage level (35.5V or lower), it outputs a reset signal
from the VDT port to CPU and ASIC.
NOTE: IC5, also serving as RIC (Real Time Clock), manages timer control when
the printer power is turned off. Power for this operation is supplied from
the BAT1.
Figure 2-19. Reset Circuit Block Diagram
N M I V D T
F R S T
R S T
C E
S C L K
D A T A
V I N
V D D
V B K
G N D
+ 4 2 V + 5 V
M R E S
R E S E T
C 2 1
0 . 1 U
C 1 9
0 . 1 U
C 1 8
0 . 1 U
T C E
T C L K
T D A T A
D 2
S B 0 0 7 - 0 3 C P T B
I C 8
E 0 5 B 7 0 C D
B A T 1
C R 2 0 3 2
+ 3 . 3 V
R 2 6
3 . 3 K
R 2 7
3 . 3 K