GS4911B Datasheet, PDF (65/119 Pages) Gennum Corporation – HD/SD/Graphics Clock and Timing Generator with GENLOCK

Table 3-9: Encoding Scheme for AFS_Reset_Window
Window Tolerance (us)
AFS_Reset_Window
(address 31h)
fs = 32kHz
fs = 44.1kHz
000
0.044
0.033
001
0.084
0.062
010
(default)
0.166
0.121
011
0.329
0.239
1XX
0.654
0.475
NOTE: ‘X’ signifies ‘don’t care.’ The bit setting will be ignored.
fs = 48 kHz
0.030
0.057
0.112
0.220
0.437
fs = 96 kHz
(enable_384fs = 1)
0.030
0.057
0.112
fs = 96 kHz
(enable_384fs = 0)
0.044
0.084
0.166
0.220
0.437
0.329
0.654
3.7.2.1 Audio to Video Clock Phasing
The important aspect of the audio to video phase relates to the way in which the AFS
pulse is used to reset the audio clock dividers so as to line up the leading edge of the
audio clocks with the leading edge of the H Sync pulse on line 1 of the first field in the
audio frame sequence. The AFS pulse is further discussed in Section 3.8.2 on page 68.
625i 50 Format
For the 48kHz sampling rate, the audio to video phase relationship for 625/50i reference
signals is provided by the device in accordance with the EBU recommended practice
R83-1996. The start of an audio frame (fs clock) will align with the 50% point of the H
sync input of line 1 of each video frame (+/- the allowable drift specified in Table 3-9).
525i 59.94 Format
For 525/59.94 NTSC reference signals, the device will observe the 5-frame
phase-relationship inherent with this video standard, aligning the audio clocks with the
50% point of the H sync input of line 1 on every fifth frame (+/- the allowable drift
specified in Table 3-9).
The number of audio sample clocks during a video frame is shown in Table 3-10 for 32,
44.1, and 48kHz audio sampling frequencies.
GS4911B/GS4910B HD/SD/Graphics Clock and Timing
Generator with GENLOCK
Data Sheet
36655 - 5
June 2009
65 of 119