Epson PhotoPC 800, Service Manual

Page: 46 / 110

EPSON PhotoPC 800 Revision A
Operating Principle Operating principles of the Circuit Boards 46
2.2.3.3 Key Operation (Key Matrix)
For details of the key operation, refer to the instruction manual.
Table 2-10. Key Operation
2.2.3.4 Power Supply Control
The 8-bit microprocessor controls the power supply for the overall system. The
following is a description of how the power supply is turned on and off. When
the battery is attached, risen up to 5 V voltage is input to the IC304 by IC303,
and regulated 3.2V voltage is normally input to the 8-bit microprocessor
(IC301) by IC304. That allows the clock to run to the camera to continue
checking the power even when the power switch is turned off, so that the
camera can start up again. When the battery is removed, the 8-bit
microprocessor operates in sleep mode using the backup super capacitor. At
this time, the 8-bit microprocessor only carries out clock counting, and waits in
standby for the battery to be attached again. When a switch is operated, the 4-
bit microprocessor supplies power to the system as required.
The 8-bit microprocessor first sets both the /P (A) ON signal at pin (71) and the
/P (A) ON signal at pin (70) to high, and then turns on the DC/DC converter.
After this, High signals are output from pins (97) and (88) so that the ASIC and
the SPARC lite are set to the active condition. If the LCD monitor is on, the pin
(95) set to LCD ON signal, and the DC/DC converter for the LCD monitor is
turned on. Once SPARC lite processing is completed, the ASIC and the
SPARC lite return to the reset condition, all DC/DC converters are turned off
and the power supply to the whole system is halted.
Table 2-11. Power Supply Control
Scan
OUT
Scan IN
0 1 2 3 4 5 6
0
SHUTTE
R 2nd
SHUTT
ER 1sr
RES0
SELF
TIMER
-- -- --
1 (TEST2)
(LCD)
TEST
FLASH
LENS
COVER
OPEN
-- -- --
2 SW1 SW2 SW3 SW4 SWC SWB SWA
3 SPECIAL LCD CAM OFF PLAY
DIRECT
PRINT
SET UP
SPARC
LITE
ASIC
MEMO
RY
Driver/
Receiv
er
CCD
8bit
CPU MODE
LCD
LCD
MONIT
OR
Supply
voltage
3.3V 3.3V 3.4V 5.0V
5V (A)
+15V-
7V
3.2V
(ALWA
YS)
3.2V
(ALWA
YS)
5V (A)
+12V
etc.
OFF OFF OFF OFF OFF OFF 32KHz OFF OFF