ADV7177KS-REEL Analog Devices Inc, ADV7177KS-REEL Datasheet - Page 35

• Manufacturer Part Number: ADV7177KS-REEL
• Description: IC DAC VIDEO NTSC 3-CH 44MQFP
• Manufacturer: Analog Devices Inc
• Type: Video Encoderr

Specifications of ADV7177KS-REEL

• Rohs Status: RoHS non-compliant
• Applications: Set-Top Boxes, TV
• Voltage - Supply, Analog: 3 V ~ 3.6 V
• Mounting Type: Surface Mount
• Package / Case: 44-MQFP, 44-PQFP
• Adc/dac Resolution: 9b
• Screening Level: Commercial
• Package Type: MQFP
• Pin Count: 44
• Voltage - Supply, Digital: -
• Lead Free Status / RoHS Status: Not Compliant

CLOSED CAPTIONING
The ADV7177/ADV7178 support closed captioning, which
conforms 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 2 data bits and is
followed by a Logic 1 start bit. The start bit is followed by16 bits
of data. 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 ADV7177/ADV7178 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
Line 21 and Line 284 are generated automatically by the
ADV7177/ ADV7178. All pixels inputs are ignored during
Line 21 and Line 284.
50 IRE
40 IRE
FREQUENCY = F
REFERENCE COLOR BURST
AMPLITUDE = 40 IRE
10.5 ± 0.25µs
10.003µs
(9 CYCLES)
SC
= 3.579545MHz
27.382µs
Figure 44. Closed Captioning Waveform (NTSC)
Rev. C | Page 35 of 44
12.91µs
FCC Code of Federal Regulations (CFR) 47 Section 15.119 and
EIA608 describe the closed captioning information for Line 21
and Line 284.
The ADV7177/ADV7178 uses a single buffering method.
This means that the closed captioning buffer is only 1 byte
deep, therefore there is 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 in turn loads the new data (2 bytes)
every field. If no new data is required for transmission, zeros
must be inserted in both 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 does not recognize them. If
you have a message such as “Hello World, ” which has an odd
number of characters, it is important to pad it out to an even
number to include the end-of-caption, 2-byte control code in
the same field.
D0–D6
33.764µs
D0–D6
ADV7177/ADV7178