ADV7312KST Analog Devices Inc, ADV7312KST Datasheet - Page 62

• Manufacturer Part Number: ADV7312KST
• Manufacturer: Analog Devices Inc

Specifications of ADV7312KST

• Number Of Dac's: 6
• Adc/dac Resolution: 11b
• Screening Level: Commercial
• Package Type: LQFP
• Pin Count: 64
• Lead Free Status / RoHS Status: Not Compliant

ADV7312
APPENDIX 3—SD CLOSED CAPTIONING
[Subaddress 51h–54h]
The ADV7312 support closed captioning conforming to the
standard television synchronizing waveform for color trans-
mission. Closed captioning is transmitted during the blanked
active line time of Line 21 of the odd fields and Line 284 of the
even fields.
Closed captioning consists of a 7-cycle sinusoidal burst that is
frequency and phase locked to the caption data. After the clock
run-in signal, the blanking level is held for two data bits and is
followed by a Logic 1 start bit. Sixteen bits of data follow the
start bit. These consist of two 8-bit bytes, seven data bits, and
one odd parity bit. The data for these bytes is stored in the SD
closed captioning registers [Address 53h–54h].
The ADV7312 also support the extended closed captioning
operation, which is active during even fields and is encoded on
Scan Line 284. The data for this operation is stored in the SD
closed captioning registers [Address 51h–52h].
All clock run-in signals and timing to support closed captioning
on Lines 21 and 284 are generated automatically by the ADV7312.
50 IRE
40 IRE
FREQUENCY = F
REFERENCE COLOR BURST
AMPLITUDE = 40 IRE
10.5
Figure 66. Closed Captioning Waveform, NTSC
10.003 s
(9 CYCLES)
0.25 s
SC
= 3.579545MHz
27.382 s
CLOCK RUN-IN
7 CYCLES OF
0.5035MHz
12.91 s
–62–
All pixels inputs are ignored during Lines 21 and 284 if
closed captioning is enabled.
FCC Code of Federal Regulations (CFR) 47 section 15.119
and EIA608 describe the closed captioning information for
Lines 21 and 284.
The ADV7312 use a single buffering method. This means that
the closed captioning buffer is only 1-byte deep; therefore
there will be no frame delay in outputting the closed captioning
data unlike other 2-byte deep buffering systems. The data must
be loaded one line before (Line 20 or Line 283) it is output on
Line 21 and Line 284. A typical implementation of this method is
to use VSYNC to interrupt a microprocessor, which in turn will
load the new data (two bytes) in every field. If no new data is
required for transmission, 0s must be inserted in both data
registers; this is called nulling. It is also important to load con-
trol codes, all of which are double bytes on Line 21, or a TV
will not recognize them. If there is a message like “Hello World”
that has an odd number of characters, it is important to pad it
out to even in order to get “end of caption” 2-byte control code
to land in the same field.
S
T
A
R
T
D0–D6
BYTE 0
TWO 7-BIT + PARITY
ASCII CHARACTERS
33.764 s
(DATA)
A
R
P
T
Y
I
D0–D6
BYTE 1
P
A
R
T
Y
I
REV. 0