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AL710

QUAD Video Processor

AverLogic Technologies Inc 

AL700/701/710

After the processed blinking data is passed to the Boolean logic operation section, the

Boolean logic operation section performs special OSD effects such as translucent, opaque,

negative, and posterization. The Boolean logic operation feature, which provides a vivid

and unique way of implementing display menu and status, is controlled by the FOREOP

(#23h) register.

The fading operation block creates the effect of smoothly fading in and fading out the

OSD titles or menu. Fading is controlled by register ALPHA (#22h).

Following is the block diagram of the AL700/701/710 OSD.

VIDEO

DATA

RSTB

CLK

HSYNC

VCNT

HCNT

OSD_CLK

OSD_VBLK

OSD_COLOR

MONOSD_EN

VCROSD_EN

C O LO R

S ELE CT

BLINKING AND

LO G IC

O P ERATION

FADING

O P ERATION

VIDEO+OSD

OSD

CONTROL

OSDKEY

COLOR0

COLOR1

COLOR2

COLOR3

FOREOP

ALPHA BLINK

OSD Registers setting

CONTEXT_RAMADDR

CONTEXT_RAMDATA

C ONTEXT_RAM 1K

FONT_RAM 4K

Figure 13: AL700/701/710 OSD Block Diagram

The Context RAM is used to store the Character code or index for accessing a specific

font (a font can be viewed as a pre-defined bitmap) stored in Font RAM. The address of

the Character code is generated first to retrieve the index address to a specific font or

bitmap. The following Font RAM address generators then calculate the address of the

font stored in Font RAM based on the Character code read from Context RAM. The 8-bit

data read from Font RAM is then unpacked into 1-bit or 2-bit data depending if 2-color

mode or 4-color mode is selected. MSB bits are read out as OSD data before the LSB bits.

This is illustrated as follows:

©2001,2002-Copyright by AverLogic Technologies, Corp. Preliminary Version C1.1 23

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