ST92196A datasheet(144/268 Pages) STMICROELECTRONICS

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- ON SCREEN DISPLAY CONTROLLER (OSD)

OSD CONTROLLER (Cont’d)

Bit 1 = ROU

Rounding control bit

This bit enables or disables the rounding for the

whole row.

0: the rounding is disabled

1: the rounding is enabled

Note: For a 18x26 matrix size, there is no rounding

when the character size is (1X,1Y). For any other

(X,Y) size combinations, the rounding is possible

for the 18x26 font matrix.

Bit 0 = FR

Fringe control bit

This bit enables or disables the fringe for the whole

row. The fringe mechanism can be activated for

any size and matrix format.

0: the character fringe is disabled

1: the character fringe is enabled.

Note: In case of fringe usage in 1Y vertical size

and interlaced mode, a flicker may appear on

screen as the fringe information is built on a field

basis.

8.5.8.4 Active Range

Address in Segment 22h: 2p + 5. See Figure 59.

The active range feature is useful for software con-

trolled smooth vertical scrolling (up or down).

For each row to be displayed, the first line (RS)

and the last line (RE) to be displayed for the cur-

rent row have to be specified.

The two values (RS[3:0] and RE[3:0]) are com-

pared to the row line counter value. If the value of

the counter is outside the active range (less than

RS[3:0] or greater than or equal to RE[3:0]), the

border color is displayed as defined by its at-

tributes. Otherwise, if the counter value is inside

the active range, the normal character pixel

processing and display is done (See Figure 66).

Let’s assume that the start address of the current

row buffer is 2p (even address).

Bits 7:4 = RS[3:0]

Active Range Start value

The RS[3:0] value range is 0h-Ch (0-12) in all cas-

es (9x13 or 18x26 character matrix).

Bits 3:0 = RE[3:0]

Active Range End value

The RE[3:0] value range is 1h-Dh (1-13) in all cas-

es (9x13 or 18x26 character matrix).

Note: For 18x26 matrix characters, the active

range is calculated by pair of TV lines, i.e. the ac-

tive range always starts on the first field and finish-

es on the second field (in interlaced mode).

In case of non-interlaced display mode, the active

range is calculated by pair of TV lines.

Figure 66. Active Range Example

RS3

RS2

RS1

RS0

RE3

RE2

RE1

RE0

RS = 0 ; RE = 13

RS = 4 ; RE = 9

ACTIVE RANGE EXAMPLE

Pixel not

displayed

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