Epson PhotoPC 3000Z, Service Manual

Page: 51 / 109

EPSON PhotoPC 3000Z Revision A
Operating Principles Circuit 51
2.2.4.2 Internal Communication Bus
The SY1 circuit board carries out overall control of camera operation by
detecting the input from the keyboard and the condition of the camera
circuits. The 8-bit microprocessor reads the signals from each sensor element
as input data and outputs this data to the camera circuits (ASIC) or to the LCD
display device as operation mode setting data. Figure 2-16 shows the internal
communication between the 8-bit microprocessor, ASIC and SPARC lite
circuits.
Figure 2-16. Internal Bus Communication System
2.2.4.3 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, a regulated 3.2 V is normally input to the 8-bit
microprocessor (IC301) by IC302, so that 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 battery is removed, the 8-bit microprocessor
operates in sleep mode using the backup 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 ON signal at pin (71) and the PA
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 LCD
ON signal at pin (95) set to high, 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.
97 ASIC RESET O
ASIC reset signal
L: Reset output
98 MAIN RESET O
SPARC reset signal
L: Reset output
99 AVSS - A/D converter GND power terminal
100 BATTERY I Battery voltage input (analog input)
Table 2-3. 8bit Micro Processor Pin Configuration
Pin Signal I/O Outline