Epson Research and Development
Page 79
Vancouver Design Center
Hardware Functional Specification
S1D13704
Issue Date: 01/02/08
X26A-A-001-04
12 SwivelView™
Many of todays applications use the LCD panel in a portrait orientation. In this case it
becomes necessary to “rotate” the displayed image. This rotation can be done by software
at the expense of performance or, as with the S1D13704, it can be done by hardware with
no CPU penalty.
There are two SwivelView modes: Default SwivelView and Alternate SwivelView.
12.1 Default SwivelView Mode
Default SwivelView Mode requires the portrait image width be a power of two, e.g. a 240-
line panel requires a minimum virtual image width of 256. This mode should be used
whenever the required virtual image can be contained within the integrated display buffer
(i.e. virtual image size
≤
40k bytes), as it consumes less power than the Alternate
SwivelView mode.
For example, the panel size is 320x240 and the display mode is 4 bit-per-pixel. The virtual
image size is 320x256 which can be contained within the 40k Byte display buffer.
Default SwivelView Mode also requires memory clock (MCLK)
≥
pixel clock (PCLK).
The following figure shows how the programmer sees a 240x320 image and how the image
is displayed. The application image is written to the S1D13704 in the following sense:
A–B–C–D. The display is refreshed by the S1D13704 in the following sense: B-D-A-C.
Figure 12-1: Relationship Between The Screen Image and the Image Refreshed by S1D13704
256
25
6
image seen by programmer
= image in display buffer
320
SwivelView
window
32
0
240
A
B
C
D
D
C
B
A
24
0
start
address
S
w
iv
el
Vi
ew
wi
nd
ow
display
E
E
image refreshed by S1D13704
start
address
physical
memory
*