RIVA128 datasheet(55/77 Pages) STMICROELECTRONICS

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128-BIT 3D MULTIMEDIA ACCELERATOR

RIVA 128

55/77

11.6 TV OUTPUT SUPPORT

Reference clock options

The RIVA 128 supports two synthesizer reference

clock frequencies; 13.5MHz and 14.31818MHz.

The reference clock frequency is determined by a

crystal or reference clock connected to the XTA-

LIN and XTALOUT pins. Where TV-out is support-

ed, XTALOUT should be driven by a 13.5MHz ref-

erence clock derived from an external NTSC/PAL

clock source as illustrated in Figure 59. The clock

frequency should match the power-on configura-

tion setting described in Section 10, page 49.

PAL/NTSC TV interface

The RIVA 128 supports TV output through an ex-

ternal Analog Devices AD722 PAL/NTSC RGB

encoder chip as shown in Figure 59. 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 RIVA

128 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 59. 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 59.

TV output implementation

Ω

RIVA 128

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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