adv7171a-dbrd Analog Devices, Inc., adv7171a-dbrd Datasheet - Page 41

• Manufacturer Part Number: adv7171a-dbrd
• Description: Digital Pal/ntsc Video Encoder With 10-bit Ssaf ?nd Advanced Power Management
• Manufacturer: Analog Devices, Inc.

APPENDIX 3—COPY GENERATION MANAGEMENT SYSTEM (CGMS)
The ADV7170/ADV7171 support copy generation management systems (CGMS) conforming to the standard. CGMS data is transmitted
on Line 20 of the odd fields and Line 283 of even fields. Bit C/W05 and Bit C/W06 control whether or not CGMS data is output on odd
and even fields. CGMS data can only be transmitted when the ADV7170/ADV7171 are configured in NTSC mode.
The CGMS data is 20 bits long; the function of each of these bits is shown below. The CGMS data is preceded by a reference pulse of the
same amplitude and duration as a CGMS bit (see Figure 57). The bits are output from the configuration registers in the following order:
C/W00 = C16, C/W01 = C17, C/W02 = C18, C/W03 = C19, C/W10 = C8, C/W11 = C9, C/W12 = C10, C/W13 = C11, C/W14 = C12,
C/W15 = C13, C/W16 = C14, C/W17 = C15, C/W20 = C0, C/W21 = C1, C/W22 = C2, C/W23 = C3, C/W24 = C4, C/W25 = C5,
C/W26 = C6, C/W27 = C7.
If the Bit C/W04 is set to a Logic Level 1, the last six bits, C19 to C14, which comprise the 6-bit CRC check sequence, are calculated
automatically on the ADV7170/ADV7171 based on the lower 14 bits (C0 to C13) of the data in the data registers and output with the
remaining 14 bits to form the complete 20 bits of the CGMS data. The calculation of the CRC sequence is based on the polynomial
X
registers (no CRC is calculated; it must be calculated by the user).
Function of CGMS Bits
Word 0
Word 1
Word 2
CRC
Word 0
B1
B2
B3
Word 0
B4, B5, B6
Word 1
B7, B8, B9, B10
Word 2
B11, B12, B13, B14
6
+ X + 1 with a preset value of 111111. If C/W04 is set to a Logic Level 0, all 20 bits (C0 to C19) are directly output from the CGMS
+100 IRE
+70 IRE
–40 IRE
– 6 Bits
– 4 Bits
– 6 Bits
– 6 Bits
0 IRE
1
Aspect Ratio
Display Format
Undefined
CRC Polynomial = X
Identification information about video and other signals (for example, audio)
Identification signal and information incidental to Word 0
Identification signal incidental to Word 0
11.2µs
0
16:94:3
Letterbox
2.235µs ± 20ns
REF
6
+ X + 1 (Preset to 111111)
C0
Figure 57. CGMS Waveform Diagram
C1
Normal
C2
Rev. B | Page 41 of 64
C3
C4
C5
C6
C7
49.1µs ± 0.5µs
C8
C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 C19
CRC SEQUENCE
ADV7170/ADV7171