Motorola MC68VZ328 - Manual (Page 133)

LCD Controller Operation
LCD Controller 8-5
Figure 8-3. LCD Screen Format
The LCD screen width (LXMAX) and LCD screen height (LYMAX) registers are where the size of the
LCD panel is specified. The LCD controller will start scanning the display memory at the location pointed
to by the LCD screen starting address (LSSA) register. Therefore, the shaded area in Figure 8-3 will be
displayed on the LCD panel.
The maximum page width and page height are specified by the LCD virtual page width (LVPW) and LCD
virtual page height parameters. By changing the LSSA register, a screen-sized window can be vertically or
horizontally scrolled (panned) anywhere inside the virtual page boundaries. However, it is up to the
programmer, through software, to position the starting address so that the scanning logic’s system memory
pointer does not stretch beyond the virtual page width or height. Otherwise, strange objects will appear on
the screen. The LVPH parameter shows the bottom of the page, but it is not used by the LCD controller.
8.2.2.2 Format of the Cursor
To define the position of the hardware cursor, the LCD controller maintains a vertical line counter (YCNT)
to keep track of the current pixel’s vertical position. YCNT, in conjunction with XCNT (the horizontal
pixel counter), specifies the screen position of the pixel data being processed. When the pixel falls within a
window specified by the cursor’s reference position, cursor width, and cursor height, the original pixel bits
can be shown with different properties. These properties can be transparent (cursor is disabled), full (black
cursor), reversed video, full (white cursor), or blinking. The hardware cursor blink can be made to blink by
setting the BKEN bit in the LBLKC register to 1, which alternates the original signal and cursor
periodically. The speed at which the cursor blinks may be controlled by selecting the BDx bit in the
LBLKC register. The half-period may be as long as 2 seconds.
Screen Width
Virtual Page Width
Screen Starting Address
V
irt
ual Page Height
Cursor X Position
Cursor Y Pos
ition
Cursor Width
C
u
rso
r He
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ht
Sc
reen Height