AN2641 datasheet(7/37 Pages) STMICROELECTRONICS

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AN2641

CLCD panel programmable parameters

Doc ID 14027 Rev 1

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CLCD panel programmable parameters

To allow the CLCD controller to interface with the CLCD panel you intend to use in your

application, you have to program a set of parameters, which varies according to the type of

CLCD. For example, some parameters depend upon CLCD dimensions and

synchronization, other parameters depend on the CLCD clock source and frequency, or the

display panel type.

2.1

Panel dimensions

This section describes the parameters and the corresponding registers that depend on the

LCD dimensions: X and Y resolution, vertical and horizontal synchronization.

2.1.1

X and Y resolution

The entire screen of CLCD is composed of pixels, each pixel a single dot. The number of

pixels along the horizontal axis forms the X-resolution and the number of pixels along the

vertical axis make up the Y-resolution. X-resolution and Y-resolution are also known

respectively as the number of pixels per line and the number of lines per panel.

Figure 1.

A basic CLCD panel

One common example is a 480 x 272 CLCD panel, which has 480 pixels horizontally and

272 pixels vertically.

2.1.2

Synchronization parameters

To draw any image on a CLCD panel, the screen is first scanned left to right is scanned and

then the screen is scanned top to bottom. After each scan-line, the electron beam has to

move back to the left side of the screen and to the next line, this is called the horizontal

retrace. After the whole screen (frame) is painted, the beam moves back to the upper left

corner, this is called the vertical retrace.

Since the CLCD panel does not know when a new scan-line starts, the CLCD controller

generates a synchronization pulse (Horizontal Sync Width) for each scan-line. Similarly, it

supplies a synchronization pulse (Vertical Sync Width) for each new frame. The position of

the image on the screen is controlled by the timing of the synchronization pulses.

X-resolution

Y-res

olution

(0.0)

(0.X)

(X,Y)

(0,Y)

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