Cirrus Logic CS4955 - Manual (Page 11)

CS4954 CS4955
DS278F6 11
2. ADDITIONAL CS4954/5 FEATURES
• Five programmable DAC output combinations,
including YUV and second composite
• Optional pseudo-progressive scan @ MPEG2
field rates
• Stable color subcarrier for MPEG2 systems
• General purpose input and output pins
• Individual DAC power-down capability
• On-chip color bar generator
• Supports RS170A and ITU R.BT601 compos-
ite output timing
• HSYNC and VSYNC output in ITU R.BT656
mode
• Teletext encoding selectable on two composite
and S-video signals
• Programmable saturation, SCH Phase, hue,
brightness and contrast
• Device power-down capability
• Super White and Super Black support
3. CS4954 INTRODUCTION
The CS4954/5 is a complete multi-standard digital
video encoder implemented in current CMOS tech-
nology. The device can operate at 5 V as well as at
3.3 V. ITU R.BT601- or ITU R.BT656-compliant
digital video input is converted into NTSC-M,
NTSC-J, PAL-B, PAL-D, PAL-G, PAL-H, PAL-I,
PAL-M, PAL-N, or PAL-N Argentina-compatible
analog video. The CS4954/5 is designed to con-
nect, without glue logic, to MPEG1 and MPEG2
digital video decoders.
Two 10-bit DAC outputs provide high quality S-
Video analog output while another 10-bit DAC si-
multaneously generates composite analog video. In
addition, there are three more DACs to provide si-
multaneous analog RGB or analog YUV outputs.
The CS4954/5 will accept 8-bit YCbCr or 8-bit
YUV input data.
The CS4954/5 is completely configured and con-
trolled via an 8-bit host interface port or an I²C
compatible serial interface. This host port provides
access and control of all CS4954/5 options and fea-
tures, such as closed caption insertion, interrupts,
etc.
In order to lower overall system costs, the
CS4954/5 provides an internal voltage reference
that eliminates the requirement for an external, dis-
crete, three-pin voltage reference.
In ISO MPEG-2 system configurations, the
CS4954/5 can be augmented with a common color-
burst crystal to provide a stable color subcarrier
given an unstable 27 MHz clock input. The use of
the crystal is optional, but the facility to connect
one is provided for MPEG-2 environments in
which the system clock frequency variability is too
wide for accurate color sub-carrier generation.
4. FUNCTIONAL DESCRIPTION
In the following subsections, the functions of the
CS4954/5 will be described. The descriptions refer
to the device elements shown in the block diagram
on the cover page.
4.1 Video Timing Generator
All timing generation is accomplished via a
27 MHz input applied to the CLK pin. The
CS4954/5 can also accept a signal from an optional
color burst crystal on the XTAL_IN &
XTAL_OUT pins. See the section, Color Subcarri-
er Synthesizer, for further details.
The Video Timing Generator is responsible for or-
chestrating most of the other modules in the device.
It operates in harmony with external sync input
timing, or it can provide external sync timing out-
puts. It automatically disables color burst on appro-
priate scan lines and automatically generates
serration and equalization pulses on appropriate
scan lines.