Lucent Technologies MN10285K - Manual (Page 157)

On-Screen Display
OSD Operation
Panasonic Semiconductor Development Company MN102H75K/F75K/85K/F85K LSI User Manual
156
Panasonic
7.5 OSD Operation
This section describes the basic operation of the OSD block. The remainder of
section 7 provides more detailed specifications.
7.5.1 OSD Clock
The OSD clock source is programmable to either the microcontroller system
clock (OSC1, OSC2 pins) or a dedicated OSD clock (OSDXI, OSDXO pins).
■ OSC clock source
See section 7.11, “Selecting the
OSD Dot Clock,” on page 186,
for information on setting the
OSD clock frequency.
An internal phase-locked loop (PLL) multiplies the external 4-MHz frequency to
generate an OSD clock that is synchronized to the trailing edge of the horizontal
sync signal (HSYNC). This dramatically reduces EMI and character distortion.
The output frequency is programmable to 12, 16, 24, 32 or 48 MHz.
■ OSDX clock source
An LC blocking oscillator allows HSYNC to serve as the clock source. You can
also input an external clock through the OSDXI pin and synchronize it internally.
(Frequency range: 12 –48 MHz)
7.5.2 External Input Sync Signals
Input the horizontal sync signal through the HSYNC pin and the vertical sync
signal through the VSYNC pin. The pullup resistors and polarity are pro-
grammable. An interrupt must occur so that the microcontroller can detect each
VSYNC start field. Set the interrupt edge in the IQ1TG[1:0] bits of the EXTMD
registers and the OSD input polarity in the VPOL bit of the OSD1 register. Note
that you must these parameters separately.
7.5.3 Multi-Layer Format
Multi-layer technology enables the microcontroller to display text, graphics, and
hardware cursor as different display layers with different color depths. You can
stack the layers in any order. When the layers contain overlapping images, the
cursor always takes highest priority. The priority of the text and graphics layers is
programmable in the registers.
■ Text layer
Do not layer any graphic or cur-
sor tiles over italicized charac-
ters in closed-caption mode.
Each character in the text layer contains a foreground (character) color and a
background color. Outlining and shadowing are separate options. In closed-
caption mode, the OSD can only display the text in the encoded captions. The
graphics and cursor layers can be displayed in this mode, but note that if any tiles
from either layer overlaps italicized text, the pixels in the graphic will be dis-
placed, distorting the image.