PCB8517 datasheet(12/24 Pages) PHILIPS

12 / 24 page

1997 Mar 03

Philips Semiconductors

Objective speciﬁcation

Stand-alone OSD for monitor applications

PCB8517

Character ROM

The character ROM contains 128 character fonts. Each

font consists of a 12

× 16 dot matrix.

Bordering and shadowing of characters

The characters displayed on the screen can be specified

with or without shadowing or with border shadowing by

setting the BSEN and SHSE bits of frame control register

“Column 11 of row 10”. If shadowing is specified, there is

black shadow on the right and bottom sides of character,

and if border shadowing is specified, the black shadowing

will surround both internal and external sides of characters

(see Fig.5). The characters shadow will not appear if it is

outside the display area of character (i.e. 12

× 16 dots).

Combination of two or more character fonts to

formulate a new symbol

User can combine two (or more) character fonts to

formulate a new higher resolution symbol in a horizontal

direction, but the combination of two fonts in a vertical

direction could cause the shadowing or bordering shadow

of upper font to be missed if shadowing or bordering is

applied.

PLL clock generator

By tracing the signal on the HFLB pin, the on-chip PLL

circuit generates the clock (VCLK) which is used for both

system clock and dot clock of the OSD. The frequency of

VCLK signal is determined by following equation:

fVCLK =fHFLB × 384 (i.e. the frequency range of VCLK

signal is from 3.84 to 38.4 MHz).

When there is no horizontal sync pulse present on the

HFLB pin, the PLL circuit will generate a 2.5 MHz

(approximate) clock for the system clock, and the RED,

GREEN, BLUE and FB pins will be high impedance.

Fig.5 Character shadowing and bordering.

handbook, full pagewidth

no shadow

shadowing

MGD759

bordering shadow

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