RIVA128ZX datasheet(61/85 Pages) STMICROELECTRONICS

61 / 85 page

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;

13.5MHz

and

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. A MicroClock

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 GND as shown in Figure 67. Alternative-

ly a clock input (e.g. ClockCan) can be connected

to X1, leaving X2 disconnected. Further details are

given in the MK2715 datasheet [8].

Figure 67.

TV output implementation

Ω

RIVA128ZX

VIDHSYNC

AD722 TV

RGB Encoder

RIN

GIN

BIN

HSYNC

FIN

YOUT

COUT

CVOUT

220

µF

220

µF

220

µF

Ω

MK2715

NTSC/PAL

Clock Source

Ω

4XCLK

REFOUT

XTALOUT

XTALIN

Ω

330

Ω

220

Ω

27pF

13.50000MHz

crystal

X1/ICLK

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