STV1602A データシートの表示（PDF） - STMicroelectronics

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STV1602A

SERIAL INTERFACE TRANSMISSION DECODER

STMicroelectronics 

STV1602A

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).

Figure 26

Input data : hex, 10-bit

(hex, 8-bit)

Serial output when

the worst sequence

on DC component

is occuring (case A)

(case B)

300 198 300 198

(CO) (66) (CO) (66)

1 bit

1 bit

19 bits

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.

Figure 27 : Particular Data words for checking

PLL bit slip

Input data : hex, 10-bit

(hex, 8-bit)

Serial output when

the worst sequence

on bit slip is occuring

110 200 110 200

(44) (80) (44) (80)

20 bits

20 bits

* 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

will, however, create an identical

sequence in the serial domain since the

difference amongst the family is merely

which bit is regarded as the start bit of a

word.

19/22

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