NEC DLP CINEMA NC1600C, Service Manual

Page: 213 / 382

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8-8
CIRCUIT DESCRIPTION
8 8 8 8 8
External control circuit
Connector POCO is a connector to make a connection with the GPIO PWB. When a control signal input is
transmitted from D-Sub Pin 37 of the GPIO terminal in the projector, it is converted into a signal maintained
at the LVTTL level via the photo coupler of the GPIO PWB. The converted signal is then entered in Pins 1 ~
7 of this POCO. This signal input passes through the buffer logic IC7800 and is entered in the PI/O circuit of
the CPU.
The CPU periodically supervises the status of this input and takes a variety of actions according to the status
of input; such as power supply startup, signal changeover, and so on.
Pins 9 ~ 14 of Connector POCO are used to supply the potential data of GND and S5.0V to actuate
the photo coupler of the GPIO PWB.
3. Setup
1 1 1 1 1
DIP switches
Two DIP switches (S7200 and S7600) are allocated on the PWB. Each has the functions as described below.
• S7200 (4p)
This switch is used for hardware debugging. In ordinary usage, it should be set at the OFF side. If it is
carelessly set at the ON side in the middle of ordinary usage, the PWB cannot operate normally.
• S7600 (2p)
This switch is used for hardware debugging. In ordinary usage, it should be set at the OFF side. If it is
carelessly set at the ON side in the middle of ordinary usage, the PWB cannot operate normally.