STW8019 datasheet(11/66 Pages) STMICROELECTRONICS

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Functional description

STw8009/STw8019

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Functional description

4.1

General

STw80x9 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.

STw80x9 is able to encode interlaced (in all standards) and non interlaced (in PAL and

NTSC) video.

STw80x9 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, STw80x9 supplies Hsync and Odd/Even sync signals (with independently

programmable polarities) to drive other blocks. STw80x9 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 STw80x9 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 STw80x9 provides a saturation limitation feature to avoid

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

distorted signal at STw80x9 CVBS or Y/C outputs.

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