Pag e 2
Circ uit De script ion
NMV 1700V
7. E
2
PROM (Circuit diagram MAIN PWB 3/10)
Data tra nsfer between I305 (AT24 C16) and CPU (Circ uit diagram MAIN PWB 2/8 (I30 2) is effected through
the IIC bus SCL (pin 15) and SDA (pin 16) of I302. The data to be transferred to each device are stored in I305.
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I315 control data.
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OSD related setting data.
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Other control data for service menu.
8. CPU circuit (Circuit diagram MAIN PWB 3/10)
I302 (87C51RD2) functions as the CPU.
The source voltage for the device is 5.0V and the system clock frequency is 24MHz.
8.1
Detection of POWER switch status
The CPU identifies the ON status of the two power supplies. The identification is made when the power supply
is turned off. For example, if the power supply is turned off with the POWER switch, the POWER switch must be
turned on when activating the power supply again. If t he power supply is tu rned off by pulling ou t the power
cord , then this p ower su pply ca n be tu rned o n by co nnectin g the power c ord, wi thout p ressin g the POWER
switch.
8.2
Display mode identification
8.2.1 Functions
(1) Display mode identification
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The display mode of input signal is identified based on Table 1.
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When the mode has been identified through the measurement of horizontal and vertical frequencies, the total
number of lines is determined with a formula of “ Horizontal frequency / Vertical frequency = Total number
of li nes. “Fina l identification c an be made by exami ning the coincidenc e of the obtained figure wit h the
number of lines fo r the mode identified from the fre quency. The boundary number of lin es in each mode is
shown in Table 2.
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When the detected frequency if the sync signal has changed, the total number of lines should be counted even
through it is rge identified frequency in the same mode.
(2) Power save mode.
This power save mode is assumed when the frequency of the horizontal / vertical signal is as specified below.
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Vertical frequen cy : 50 ~ 86 Hz
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Horizontal frequency : 24 ~ 92 KHz
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VTOTAL : 1200 or more.
(3) Power save mode.
The power save mode is assumed when the horizontal / vertical signals are as specified below.
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If there is no horizontal sync signal input.
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If there is no vertical sync signal input.
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If the horizontal sync signal is outside the measuring range of gm5020.
