User`s manual

PK2200 System Development s 47
ON/OFF - When the ON/OFF bit is set ( 1 ) the display is on, any image
on the screen will be visible. When the bit is reset ( 0 ) any images on the
display will not be visible. The image is still in the display memory.
RESET - Resets the LCD module when low ( 0 ).
Bitmapped Graphics
Many of the Dynamic C functions that operate on the graphic LCD use
bitmaps. These bitmaps represent the images on a section of the display.
An individual dot, or pixel, is represented by one bit in the bitmap. If the
pixel is on, the corresponding bit is set. If the pixel is off, the correspond-
ing pixel is reset.
The image on the display is two-dimensional (width and height). The
bitmap used to store that display information is a one-dimensional array.
Two-dimensional images are stored in column major, byte aligned bitmap
format.
Column major means that bits are stored in the bitmap column by column.
The first pixel of the first column (row 0, column 0) of the image is stored
in the first bit position in the bitmap. The second pixel of the first column is
stored in the second bit position in the bitmap and so on. When the entire first
column is stored in the bitmap, the process begins again with the second
column and repeats until all columns of the image are stored.
Byte aligned means that a column data will end on a byte boundary. If a
column has a number of bits that is not evenly divisible by eight, then the
remaining bits of the last byte representing a column will be left unused.
Image data from the next column will be stored starting in the next byte.