NEC MultiSync 3D JC-1404HME Service Manual page 61

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Automatic Synchronization
The monitor automatically synchronizes for the following frequency range.
Fh: 15.5 kHz to 38.0 kHz
Fv: 50.0 Hz to 90.0 Hz
The CPU counts the horizontal pulses during a given period of time and vertical period. After these
measurements, the corresponding digital data are produced and converted by the DAC to analog
voltage. This combination of the CPU and DAC produce frequency to voltage (F/V) converter. The
analog voltage is used as the control signal for the automatic synchronizing circuitry.
2. Automatic Display
a. Automatic signal identification
The CPU checks the input signal (TTL or ANALOG video, separate or composite SYNC, SYNC
polarity, and etc.) and automatically identifies this input signal.
*See the Fig. 2-5-2 for the Signal Identification Flowchart.
b. Automatic centering and sizing
After the CPU identifies the input signal, the CPU send the stored digital data from the correspond-
ing memory block in the EE-PROM. The EE-PROM has several memory blocks which consist of the
control data for horizontal and vertical, centering and sizing. The control data is converted to the
analog voltage by the DAC and is used by control signal.
The EE-PROM data is adjusted for the several standard signals (see Fig. 2-5-4) at the factory to get
the optimum video display area. When the end user connects a standard signal (i.e. VGA. EGA
etc.), the monitor will display the centered active video area with suitable size automatically.
c. User controls
The user can change the control data (display size and location) by pushing the proper user control
bottons. After a few seconds, the CPU will automatically store data in the EE-PROM. The user
can reset the data of the memory area and recall the initial data.
In case the user has a 3rd party's compatible board, small adjustments by the user control bottons
may be needed at the initial start up. This data information is again stored in the memory. No
adjustments are necessary after initial start up, if the same video signal is re-used.
In case a completely different video signal is applied to the monitor, the CPU will identify the
signal and select a memory block accordingly. If the display size and location are not satisfactory,
the user can adjust the display and after 5 seconds the CPU will again store the control data into
the memory.
d. Factory Adjustment
In order to simplify the display adjustments, the CPU has the PRESET factory data in its ROM.
At the beginning of the adjustment process, the CPU writes the PRESET factory data from the
ROM to the buffer RAM and then outputs them to the D/A converter. Then, the monitor is roughly
adjusted for the display size and location.
The fine adjustments are then made by adjusting the user controls by the factory personnel.
*Final adjustment process for the display size and location.
1. Prepare for the adjustment mode by shorting TP151 an.fl TPl 52. The CPU applies the PRESET
factory data to the buffer RAM and then to the D/ A converter.
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