ViewSonic VA502mb-1 Service Manual page 15

AIC1084-33PM (U202): DC power convert, used to 5v convert 3.3v.
RT9164-25PL (U201): DC power convert, used to 5v convert 2.5v.
W78E065A40PL (U601):
The W78E65 is an 8-bit microcontroller which has an in-system programmable Flash EPROM for
firmware updating. The instruction set of the W78E65 is fully compatible with the standard 8052.
The W78E65 contains a 64K bytes of main ROM and a 4K bytes of auxiliary ROM which allows
the contents of the 64KB main ROM to be updated by the loader program located at the 4KB
auxiliary ROM; 256+1K bytes of on-chip RAM; four 8-bit bi-directional and bit-addressable I/O
ports; an additional 4-bit port P4; three 16-bit timer/counters; a serial port. These peripherals are
supported by a eight sources two-level interrupt capability. To facilitate programming and
verification, the ROM inside the W78E65 allows the program memory to be programmed and
read electronically. Once the code is confirmed, the user can protect the code for security.
The W78E65 microcontroller has two power reduction modes, idle mode and power-down mode,
both of which are software selectable. The idle mode turns off the processor clock but allows for
continued peripheral operation. The power-down mode stops the crystal oscillator for minimum
power consumption. The external clock can be stopped at any time and in any state without
affecting the processor.
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