STV1602A datasheet(19/22 Pages) STMICROELECTRONICS

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Input data : hex, 10-bit

(hex, 8-bit)

Serial output when

the worst sequence

on DC component

is occuring (case A)

(case B)

300

(CO)

198

(66)

300

(CO)

198

(66)

19 bits

1 bit

Figure 26

Input data : hex, 10-bit

(hex, 8-bit)

Serial output when

the worst sequence

on bit slip is occuring

110

(44)

200

(80)

110

(44)

200

(80)

20 bits

Figure 27 : Particular Data words for checking

PLL bit slip

Using particular codes to check overall perform-

ance

Althrough the scrambling method employed effec-

tively randomizes the incoming data and puts out

a signal with a nearly uniform spectrum, there still

exist some combinations of codes that give some-

what unfriendly conditions to the transmission path

in terms of low frequency component or of a long

run without any transitions.

As shown in Figure 26, it is known that if the code

words 300, 198 (hex, 10-bit) are given alternately

to the parallel input of the encoder, the largest

amount of DC component (nearly one TV line

period) can be produced at some place with a

certain probability (such a sequence is, however,

destroyed when different data is input to the en-

coder).

Even with such signals, error-free reception is pos-

sible with the STV1602Aif a proper implementation

is made (refer to section 12 for a recommended

circuit).

Another particular combination of words, but with a

different nature, is 200, 110 (hex, 10-bit) which can

generate the sequence which is most vulnerable*

to bit slip of nearly one TV line period. Figure 27

illustrates such a situation. Similar to the previous

case, the worst sequence stops upon an arrival of

a data other than the alternating 200, 110 at the

input of the encoder.

* Stricly speaking the longest isolated run is 38

clocks for 4:2:2 and 43 clocks for 4 fsc NTSC

and PAL. However, the above sequence

generally shows the most critical situation for

the bit slip problem.

Note : Actually there exists a family of such

particular code as above described. They

w ill , h owever, cre at e an identi cal

sequence in the serial domain since the

difference amongst the family is merely

which bit is regarded as the start bit of a

word.

STV1602A

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