ADV7170SU AD [Analog Devices], ADV7170SU Datasheet - Page 33

• Manufacturer Part Number: ADV7170SU
• Manufacturer: AD [Analog Devices]

The ADV7170/ADV7171 supports Copy Generation Management System (CGMS) conforming to the standard. CGMS data is
transmitted on Line 20 of the odd fields and Line 283 of even fields. Bits C/W05 and 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 is configured in NTSC
mode. The CGMS data is 20 bits long, the function of each of these bits is as shown below. The CGMS data is preceded by a refer-
ence 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 “1,” the last six bits, C19–C14, which
comprise the 6-bit CRC check sequence, are calculated automatically on the ADV7170/ADV7171 based on the lower 14 bits
(C0–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
Logic “0,” all 20 bits (C0–C19) are directly output from the CGMS registers (no CRC calculated, must be calculated by the user).
Function of CGMS Bits
Word 0 – 6 Bits
Word 1 – 4 Bits
Word 2 – 6 Bits
CRC
Word 0
B1
B2
B3
Word 0
B4, B5, B6
Word 1
B7, B8, B9, B10
Word 2
B11, B12, B13, B14 Identification signal and information incidental to Word 0
REV. 0
– 6 Bits
100 IRE
–40 IRE
70 IRE
1
Aspect Ratio
Display Format
Undefined
0 IRE
CRC Polynomial = X
Identification information about video and other signals (e.g., audio)
Identification signal incidental to Word 0
11.2 s
0
16:94:3
Letterbox
COPY GENERATION MANAGEMENT SYSTEM (CGMS)
2.235 s
6
+ X + 1 (Preset to 111111)
REF
Normal
Figure 57. CGMS Waveform Diagram
20 s
C0
C1
C2
APPENDIX 3
C3
–33–
C4
6
+ X + 1 with a preset value of 111111. If C/W04 is set to a
C5
C6
C7
49.1 s
C8
C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 C19
0.5 s
ADV7170/ADV7171
CRC SEQUENCE