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PCA8514

Stand-alone OSD

Philips Electronics 

Philips Semiconductors

Stand-alone OSD

Product specification

PCA8514

8 DISPLAY RAM ORGANIZATION

The display RAM is organized as 256 × 12 bits. The

general format of each RAM location is as follows.

Bits <11-5> hold character data and allow a choice from

125 customer designed character fonts to be selected or

one of three reserved codes. Bits <4-0> contain the

attributes of the character font, for example colour,

character size etc.

8.1 Description of display RAM codes

There are four data formats for display RAM code:

1. Character Font Code

2. Test Code

3. Carriage Return Code

4. Space Code.

The above data formats allow great flexibility in the

creation of On Screen Displays; see Fig.8.

8.1.1 CHARACTER FONT CODE

If bits <11-5> are in the range (00H to 7CH), then this is a

Character Font Code. 1 of 125 customer designed

character fonts can be selected. Bits <4-1> determine the

colour of the character, a choice of 16 colours being

available. Bit <0> determines whether the character blinks

or not. The format of the Character Font Code is shown in

Table 2.

8.1.2 TEST CODE

If bits <11-5> hold 7DH, then this is a special code

reserved for testing purposes only.

8.1.3 CARRIAGE RETURN CODE

If bits <11-5> hold 7EH, then this is the Carriage Return

Code. A transparent pattern will be displayed on the

screen and the next character will be displayed at the

beginning of the next line. Bits <4-3> select the size of the

characters to be displayed on the next line. Bits <2-1>

determine the spacing between lines of displayed

characters. Bit <0> is the End of Display bit and indicates

the end of display of the current screen before exhaustion

of display RAM (i.e. before the 256th RAM location). The

format of the Carriage Return Code is shown in Table 3.

8.1.4 SPACE CODE

If bits <11-5> hold 7FH, then this is the Space Code.

A transparent pattern, equal to one character width, will be

displayed on the screen. A mask programmable option is

available that allows the space character to be transparent

or to have a programmable background colour;

see Section 13.1. Bits <4-1> determine the background

colour of the characters that follow the Space Code in both

the Box shadowing and North-West shadowing modes.

Bit <0> is the Active Character Monitor (ACM)

enable/disable bit. The ACM signal is specifically for use in

camrecorder applications where part of the display is to be

recorded on tape and displayed on the screen, whilst the

remaining part is for display only. Figure 9 shows a typical

ACM application. During the back-tracing period R, G, B, I,

FB and ACM are inactive. The format of the Space Code

is shown in Table 4.

Table 2 Format of Character Font Code

11

10

9

8

7

6

5

4

3

2

1

0

C6

C5

C4

C3

C2

C1

C0

T4

T3

T2

T1

T0

Character Font Code (00H - 7CH)

Foreground colour

Blink

Table 3 Format of Carriage Return Code

11

10

9

8

7

6

C6

C5

C4

C3

C2

C1

Carriage Return Code (7EH)

5

4

3

2

1

0

C0

T4

T3

T2

T1

T1

Character size

Line Spacing

End

Table 4 Format of Space Code

11

10

9

8

7

6

5

4

3

2

1

0

C6

C5

C4

C3

C2

C1

C0

T4

T3

T2

T1

T0

Space Code (7FH)

Background colour

ACM

1995 Nov 27

11

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