NXP Semiconductors LPC24XX UM10237 - Manual (Page 296)

UM10237_4 © NXP B.V. 2009. All rights reserved.
User manual Rev. 04 — 26 August 2009 296 of 792
NXP Semiconductors
UM10237
Chapter 12: LPC24XX LCD controller
With FrameSync inactive, the cursor responds immediately to any change in the
programmed CRSR_XY value. Some transient smearing effects may be visible if the
cursor is moved across the LCD scan line.
With FrameSync active, the cursor only updates its position after a vertical
synchronization has occurred. This provides clean cursor movement, but the cursor
position only updates once a frame.
6.5.5 Cursor clipping
The CRSR_XY register (see Cursor XY Position register) is programmed with positive
binary values that enable the cursor image to be located anywhere on the visible screen
image. The cursor image is clipped automatically at the screen limits when it extends
beyond the screen image to the right or bottom (see X1,Y1 in
Figure 12–38 ). The checked
pattern shows the visible portion of the cursor.
Because the CRSR_XY register values are positive integers, to emulate cursor clipping
on the left and top of screen, a Clip Position register, CRSR_CLIP, is provided. This
controls which point of the cursor image is positioned at the CRSR_CLIP coordinate. For
clipping functions on the Y axis, CRSR_XY(X) is zero, and Clip(X) is programmed to
provide the offset into the cursor image (X2 and X3). The equivalent function is provided
to clip on the X axis at the top of the display (Y2).
For cursors that are not clipped at the X=0 or Y=0 lines, program the Clip Position register
X and Y fields with zero to display the cursor correctly. See Clip(X4,Y4) for the effect of
incorrect programming.
Fig 38. Cursor clipping
Clip(X2)
Clip
(Y
2
)
Clip(X3)
C
u
rs
or
(Y
1)
Cursor(X1)
Cursor(X5)
Clip(X4)
Curs
or(Y5)
Clip(Y
4
)