SDA9488X datasheet(13/87 Pages) MICRONAS

13 / 87 page

SDA 9488X

SDA 9588X

System Description

Micronas

4-13

Preliminary Data Sheet

4.2

Inset Synchronization

Horizontal and vertical sync pulses are separated after elimination of the high frequency

components of the CVBS signal by a low pass filter. Horizontal sync pulses are

generated by a digital phase-locked-loop (DPLL). Its time constant is adjustable between

fast and slow behavior in four steps (PLLITC) to consider different input sources (e.g.

VCR). Noisy input signals become more stable when a noise-reduction is enabled

(NSRED). Additionally weak input signals from a satellite dish (’fishes’) become more

stable when SATNR is enabled. Both should be enabled to have best available

performance. When NOSIGB is enabled, a colored background is shown instead of the

picture when PIP is out of synchronization. The detected line standard is indicated by

SYNCSTAT.

4.3

Chroma Decoding And Standard Search

The system is able to decode NTSC and PAL signals with a subcarrier of 3.58MHz and

4.43MHz (PAL B/M/N/60, NTSC M/4.4) as well as SECAM signals with 4.05/4.2MHz

subcarrier. The system may be forced to a certain standard, or an automatic standard

detection can be used (CSTAND). For automatic standard detection, some standards

which are not likely to be received can be ignored to improve the detection process.

Depending on the detected line standard (525 or 625 lines) the color standard detection

circuit searches for 60 Hz signals (NTSC-M / PAL-M / PAL 60 / NTSC44) or 50 Hz signals

(PAL-B / SECAM / PAL-N) respectively. Within each line standard, the standard is

detected by consequently switching from one to another. This standard detection

process can be set to medium or fast behavior (LOCKSP). In medium behavior 30 fields

(in fast 20) are used to detect the standard. If not being successful within this time period

the system tries to detect another one. For SECAM detection, a choice between two

recognition levels is possible (SCMIDL) and the evaluated burstposition is selectable

(BGPOS).

Table 4-3

Considered color standards for automatic standard detection

For getting the chrominance information the digitized video signal is multiplied with the

regenerated color subcarrier once in-phase and once phase-shifted by 90°. After

lowpass filtering digital UV is available for PAL and NTSC. The subcarrier is regenerated

CSTANDEX

NTSC-

PAL60

PAL-N

PAL-M

PAL-B

SECAM

NTSC

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