Nikon COOLPIX S550 Repair Manual page 82

3. Key Operaiton
For details of the key operation, refer to the instruction manual.
SCAN
IN
SCAN
OUT
0
RIGHT
1
DOWN
2
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, IC501 is operating and
creating 3.9 V (POWER ON: 3.9 V → 5.0 V), a regulated 3.2 V voltage is normally input to the 8-bit microprocessor (IC301) by
IC302, clock counting and key scanning is carried out even when the power switch is turned off, so that the camera can start up
again.
When the power switch is off, the 8-bit microprocessor halts 4 MHz of the built-in main clock, and operates 32.768 kHz of
subclock.
When the battery is removed, the 8-bit microprocessor halts 4 MHz of the built-in main clock, and operates clock counting by
32.768 kHz of sub clock.
Also, the battery for backup is charged 10 hours from it to be attached.
When the power switch is on, the 8-bit microprocessor starts processing. The 8-bit microprocessor first sets the PON signal at
pin (27) to High, and then turn on the power circuit. After PON signal is to High, sets external port of ASIC after approximately 40
ms. According to setting of this external port, carry out setting of the operating frequency and oscillation control in the ASIC. Also,
it starts communication with ASIC, and confirms the system is operative.
When the through image is operating, set the PAON signal (ASIC) and PAON4 signal (ASIC) to High and then turn on the CCD.
When the through image is playing, set the PAON signal and PAON4 signal to Low and then turn off the CCD. When LCD panel
turns on, set BL ON signal (ASIC) to High, and turn on the backlight power.
When the power switch is off, PON, PAON, PAON4 and BLON signals to Low and the power supply to the whole system is halted.
The 8-bit microprocessor halts oscillation of the built-in main clock, and set operation mode of clock ocillation.
Power supply voltage
Power OFF
Through image
Playback mode
1
0
UP
LEFT
-
DEL
Table 4-2. Key Operation
Table 4-3. Power supply control
- E･ S550 -
2 3
MODE TEST
- PW_TEST
MENU
-
ASIC,
CCD
memory
1.2 V, 1.8 V 13.0 V, -7.5 V
3.2 V 3.5 V
OFF
OFF
ON ON
ON OFF
– 9 –
INC
VMA21024-R.3750.A
8bit
LCD
CPU
MONITOR
3.2 V 3.25 V
32.768 KHz OFF
4MHz ON
4MHz
ON