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NI Digital System Development Board User Manual
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© National Instruments
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35
In order to facilitate the dimming of the back-light on the LCD, the FP6745 LED driver has been
used. The user has direct access to the enable pin of the LED-driver; by driving this pin with a
PWM signal the user will obtain a variety of back-light intensities dependent on the duty cycle
of the PWM signal. When driving the back-light with PWM, it is highly recommended to choose
a PWM frequency above 20 kHz, because this circuit may interfere with the audio circuit. Before
starting to use the LCD, the DISP pin must be set to logic high. This pin is an enable pin which
allows the user to turn off the display without interrupting the timing and data flow. When
sending data to the display, the following timing specifications must be respected:
Figure 14.
Horizontal Timing
31
TFT_DISP
Display enable, active high
32
TFT_HS
Horizontal synchronisation pulse
33
TFT_VS
Vertical synchronisation pulse
34
TFT_DE
Active video signal
35
NC
Not connected
36
GND
Ground
37 - 40
NC
Not connected
Table 16.
Horizontal Timing
Horizontal Input Timing
Parameter
Symbol
Value
Unit
Min.
Typ.
Max.
Active Area
thd
—
800
—
CLKIN
CLKIN frequency
fclk
—
33.3
50
MHz
Horizontal line period
th
862
1056
1200
CLKIN
Table 15.
LCD Control Signals (Continued)
Pin
Signal
Description