ADV7176AKSZ Analog Devices Inc, ADV7176AKSZ Datasheet - Page 30

• Manufacturer Part Number: ADV7176AKSZ
• Manufacturer: Analog Devices Inc

Specifications of ADV7176AKSZ

• Adc/dac Resolution: 10b
• Screening Level: Commercial
• Package Type: MQFP
• Pin Count: 44
• Lead Free Status / RoHS Status: Compliant

ADV7175A/ADV7176A
The ADV7175A/ADV7176A supports closed captioning, conforming to the standard television synchronizing waveform for color
transmission. Closed captioning is transmitted during the blanked active line time of Line 21 of the odd fields and Line 284
of 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 Level “1” start bit. 16 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 closed captioning Data
Registers 0 and 1.
The ADV7175A/ADV7176A also supports 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 closed captioning extended Data Registers 0 and 1.
All clock run-in signals and timing to support closed captioning on Lines 21 and 284 are generated automatically by the ADV7175A/
ADV7176A. All pixels inputs are ignored during Lines 21 and 284.
FCC Code of Federal Regulations (CFR) 47 Section 15.119 and EIA608 describe the closed captioning information for Lines
21 and 284.
The ADV7175A/ADV7176A uses a single buffering method. This means that the closed captioning buffer is only one 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 at least one line before (Line 20 or Line 283) it is outputted on Line 21 and Line 284. A typical implementation of
this method is to use VSYNC to interrupt a microprocessor, which will in turn load the new data (two bytes) every field. If no new
data is required for transmission you must insert zeros in both the data registers; this is called NULLING. It is also important to load
“control codes,” all of which are double bytes on Line 21, or a TV will not recognize them. If you have a message like “Hello World”
which has an odd number of characters, it is important to pad it out to an even number to get “end of caption” 2-byte control code to
land in the same field.
40 IRE
50 IRE
REFERENCE COLOR BURST
FREQUENCY = F
AMPLITUDE = 40 IRE
10.5
(9 CYCLES)
10.003 s
0.25 s
SC
= 3.579545MHz
27.382 s
CLOSED CAPTIONING
(CLOCKRUN-IN)
APPENDIX 2
OF 0.5035 MHz
7 CYCLES
12.91 s
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