128-BIT 3D MULTIMEDIA ACCELERATOR
RIVA128ZX
61/85
11.6 TV OUTPUT SUPPORT
Reference clock options
The RIVA128ZX supports two synthesizer refer-
ence
clock
frequencies;
14.31818MHz. The reference clock frequency is
determined by a crystal or reference clock con-
nected to the
XTALIN
and
XTALOUT
pins. Where
TV-out is supported,
XTALOUT
should be driven
by a 13.5MHz reference clock derived from an ex-
ternal NTSC/PAL clock source as illustrated in
Figure 67. The clock frequency should match the
power-on configuration setting described in Sec-
tion 10, page 55.
PAL/NTSC TV interface
The RIVA128ZX supports TV output through an
external Analog Devices AD722 PAL/NTSC RGB
encoder chip as shown in Figure 67. AMicroClock
Figure 67.
TV output implementation
13.5MHz
and
MK2715 NTSC/PAL clock chip provides a com-
mon source for synchronization of the pixel and
subcarrier clocks. In TV output modes the
RIVA128ZX
XTALOUT
pin must be externally
driven from the MK2715 reference clock output,
with
XTALIN
tied to GND.
The MK2715 requires a number of external com-
ponents for proper operation. For crystal input a
parallel resonant 13.5000MHz crystal is recom-
mended, with a frequency tolerance of 50ppm or
better. Capacitors should be connected from X1
and X2 to GNDas shown in Figure 67. Alternative-
ly a clock input (e.g. ClockCan) can be connected
to X1,leaving X2disconnected. Furtherdetails are
given in the MK2715 datasheet [8].
75
75
75
RIVA128ZX
R
G
B
VIDHSYNC
AD722 TV
RGB Encoder
RIN
GIN
BIN
HSYNC
FIN
YOUT
COUT
CVOUT
220
μ
F
220
μ
F
220
μ
F
75
MK2715
NTSC/PAL
Clock Source
X2
33
4XCLK
REFOUT
XTALOUT
XTALIN
33
330
220
5V
27pF
27pF
13.50000MHz
crystal
X1/ICLK