STW8019 datasheet(10/55 Pages) STMICROELECTRONICS

10 / 55 page

Functional description

STw8009/STw8019

10/55

Functional description

4.1

General

STw8009/STw8019 operates either in master mode where it supplies all sync signal or in

slave mode.

The digital input is an 8-bit bus carrying Y, Cb and Cr at 13.5 MHz. Input samples are

latched in on the rising edge of the clock input signal.

STw8009/STw8019 is able to encode interlaced (in all standards) and non interlaced (in PAL

and NTSC) video.

STw8009/STw8019 outputs interlaced or non-interlaced video in PAL-B,D,G,H,I,PAL-N,PAL-

M or NTSC-M standards (“NTSC-4.43” is also possible).

The burst sequences are internally generated, subcarrier generation being performed

numerically with the 27 MHz as reference. 4-frame bursts are generated for PAL or 2-frame

bursts for NTSC. Rise and fall times of synchronization tips and burst envelope are internally

controlled according to the relevant ITU_R and SMPTE recommendations.

4.2

Master & slave modes

In master mode, STw8009/STw8019 supplies Hsync and Odd/Even sync signals (with

independently programmable polarities) to drive other blocks. STw8009/STw8019 starts

encoding and counting clock cycles as soon as the master mode has been loaded into the

control register (Reg 0). Configuration bits “Syncout_ad[1:0]” (Reg 4) allow to shift the

relative position of the sync signals by up to 3 clock cycles to cope with any YcbCr phasing.

In slave modes, several modes are available, Odd/Even+Hsync based, Vsync+Hsync

based, Odd/Even-only based, Vsync-only based or Sync-in-data based.

4.3

Auto test mode

An auto test mode is available, which causes STw8009/STw8019 to produce a color bar

pattern, in the appropriate standard, independently from the video input.

4.4

Input demultiplexor

The incoming YcbCr 4:2:2 data are demultiplexed into chroma information stream, a “blue-

difference” and a “red-difference”, and a luma information stream. Incoming data bits are

treated as blue, red or luma samples according to their relative position with respect to the

sync signals. Brightness, Saturation and Contrast are then performed on demultiplexed

data.

The ITU-R601 recommendation defines the black luma level as Y=16dec and the maximum

white luma level as Y=235dec. Similarly it defines 255 quantification levels for the color

difference components (Cr, Cb) centered around 128. Accordingly, incoming YcbCr samples

can be saturated. In this case STw8009/STw8019 provides a saturation limitation feature to

avoid having heavily saturated signal before digital to analog conversion and to avoid

generating a distorted signal at STw8009/STw8019 CVBS or Y/C outputs.

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