Epson Stylus CX3700 Service Manual page 58

EPSON Stylus CX3700/CX3800/CX3805/CX3810/DX3800/DX3850
2.4.2.4 Combination Circuit
This printer differs from previous models by using a combination IC that integrates the
reset circuit, EEPROM and RTC.
Reset Circuit
RTC IC (IC7) on the Main Board monitors the three voltage: +3.3V for the logic line,
+5V for the logic line and +42V for the drive line. Reset Circuit outputs the reset signal
to CPU (IC8) in the following case.
+3.3V line reset circuit
The 3.3V line is monitored at the VDD port of IC7, and if an abnormal voltage is
detected, a reset signal for the CPU is output from the FRST port of IC7.
+5V line reset circuit
The 5V line is monitored at the VDD2 port of IC7, and if an abnormal voltage is
detected, a reset signal for the CPU is output from the RST port of IC7.
+42V line reset circuit
The 42V line is monitored at the VEX port of IC7, and if an abnormal voltage is
detected, a reset signal for the CPU is output from the EXO port of IC7.
EEPROM Control Circuit
When the printer power is turned off, the following information is stored in EEPROM
(IC7) which is nonvolatile memory. And, when the printer power is on, CPU (IC8)
reads the information from EEPROM.
Information stored in EEPROM is listed below.
Various ink counter (I/C consumption counter, Waste Ink Pad counter, etc.)
Mechanical setting value (Head ID, Bi-D Adjustment, USB ID, etc.)
EEPROM is connected to CPU with 4 lines and each line has the following function.
CE : Chip selection signal
CLK : Data synchronism clock pulse
DI : Data writing line (serial data) at power off.
DO : Data reading line (serial data) at power on.
OPERATING PRINCIPLES
RTC Circuit
By adoption of the large-capacity capacitor (C9) for timer, the Power-off timer can be
backed up for about one week after power-off.
+42V +5V
C9
Electrical Circuit Operating Principles
+3.3V +3.3V
RTC
(IC7)
14 5
VDD CE
12 4
VI5 CLK
8 3
VDD2 DI
10 2
VEX DO
9
EXO
7 13
VSS FRST
11
RST
Figure 2-21. RTC Circuit Block Diagram
Revision A
+3.3V
CPU
(IC8)
A18
TCE
B18
TCLK
A17
TDO
B17
TIMDI
E18
NMII
C18
MRES
D18
RESET
58