Datasheet

 2011 Microchip Technology Inc. DS01368A-page 13
AN1368
Frame Buffer Size
The size of the frame buffer is calculated as follows:
EQUATION 2:
Table 3 shows an example for the QVGA (320x240)
display. If the double-buffering technique is used, the
frame buffer requirement will double (see Appendix B:
“Double-Buffering” for more information).
If the frame buffer is inside the display controller or the
smart display module, and if the RAM is fixed, the
maximum resolution that can be supported is limited.
Processing Power (MIPS)
The processing power required is application-specific.
It depends on how many graphic elements are
displayed on the screen and the complexity of the
graphic elements. More processing power is required
to draw complex shapes, such as a circle, bevel, text,
etc., rather than lines and rectangles. The processing
power requirements also depend on if a hardware
graphics accelerator is available and used. Processing
power requirements also depend on the update rate of
the screen elements. For many embedded graphics
applications, ≥ 16 MIPS processing power could be
sufficient. The best way to check the processing power
requirements is to evaluate using the standard
graphics development tools. (For more information on
development tools, see the “Development Tools”
section.
Configuration of Graphics Components
In Table 2, each configuration has its own advantages
and disadvantages.
Most often, the decision to use one or another
configuration is not influenced by the technical advan-
tages or disadvantages, but rather by a supply chain
advantage or the availability of components. The
designer must balance between optimizing a design to
meet the requirement and managing the supply chain.
Frame Rate VS. MIPS
Frame rate refers to the number of different frames that
can be displayed in a second. This is a good
performance index for display of a video, but not for an
embedded GUI application. In general, an embedded
application does not always change the entire screen,
instead it changes a part of the screen, like a button or
a check box. The amount of change depends on the
size of the changed widget. The update time also
depends on factors, such as if the change belongs to a
widget or an image. It is important to consider the
worst-case scenario on the planned application. Initial
calculation of frame rate and MIPS is important to get
the preliminary requirements for the system. In addition
to these calculations, it is recommended to evaluate
the system using development tools, such as
evaluation kits.
Frame Buffer (Bytes) = Total_number_of_pixels x
Color_Depth (in BPP)/8