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3. Schematics
3-5-4.
Power Supply Control
The 8-bit microprocessor controls the power supply for the entire system. This section discusses the starting and stopping of
the power supply.
When batteries are loaded, 3.2-volt power regulated by IC302 is supplied to the 8-bit microprocessor (IC301).
Even when the Power switch is set to OFF, the microprocessor runs the clock and scans the keys in preparation for the next
startup. When the power is OFF, the microprocessor stops the internal main clock (4 MHz) and runs on the sub-clock (32.768
kHz).
When the power supply batteries are removed, the microprocessor stops the 4 MHz internal main clock and runs the clock
only using the 32.768 kHz sub-clock used for the time. The microprocessor charges the backup battery for 10 hours after the
battery is installed.
When you set the Power switch to ON, the microprocessor initiates startup processing. First, it sets PON (pin 30) to High and
activates the power circuit.
Roughly 70 ms after setting PON to High, it sets the external port for the ASIC. This external port setting is then used to set
the ASIC internal operating frequency and carry out oscillation control. It then begins communication with the ASIC and checks
that the system is ready to run.
When the live image is displayed, it sets PAON (ASIC) to High and activates the CCD power supply.
During playback, it sets PAON to Low and turns the CCD power supply off. When the LCD panel is lit, it sets BLON (pin 43) to
High and turns on the backlight.
When the power is turned off, the microprocessor sets both PON and BLON Low and stops the power supply to the system.
The microprocessor stops the main clock oscillation and switches to clock oscillation operation mode.
Power supply voltage
At PW_OFF
When the live image
is displayed
In playback mode
3-8
ASIC, memory
1.2V, 1.8V, 3.2V
13.0V, -7.5V, 3.5V
OFF
ON
ON
<Table 3-4. Power supply control>
Confidential: FUJIFILM Service Center Use Only
FinePix S5800/S800 Service Manual
CCD
8bit CPU
3.2V
OFF
32.768KHz
ON
4MHz
OFF
4MHz
LCD MONITOR
3.25V
OFF
ON
ON
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