Minimizing A Retained Image On The Lcd - Sharp LH79524 User Manual

Color Liquid Crystal Display Controller

4.3.9.1 Minimizing a Retained Image on the LCD

While it is very important to follow the power turn-off sequence to ensure longevity of the
LCD panel, this sequence alone will not ensure there is no retained image (ghosting) left
on the LCD panel after the LCD has been powered down.
This ghost bleeds away slowly after powering down the LCD panel. It is most noticeable
with LCD panels utilizing HR-TFT and AD-TFT technologies to light the LCD. With these
types of LCD panels the ambient light alone is enough to make the retained image visible.
TFT-type LCD panels also have a retained image, but it is typically not as visible once the
backlight source is turned off.
To minimize the appearance of a retained image on HR-TFT and AD-TFT LCD panels,
software should write a complete frame of all 1s (white) to the LCD just prior to initiating
the turn-off sequence.
To minimize the appearance of a retained image on a TFT LCD panel, software should
write a complete frame of all 0s (black) just prior to initiating the turn-off sequence.
In all cases the illumination source should be turned off prior to initiating the turn-off
sequence.
4.3.10 Interrupts
The single combined interrupt, CLCDINTR, is used to drive the VIC. If any of the four inter-
rupt conditions occurs, this signal is asserted. CLCDINTR drives the VIC.
Each of the four individual maskable interrupt conditions is enabled or disabled by chang-
ing the mask bits in the INTREN Register. Provision of individual outputs, along with a
combined interrupt output, allows the use of either a global interrupt service routine or
modular device drivers to handle interrupts. The status of the individual interrupt sources
can be read from the Status Register.
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LH79524/LH79525 User's Guide