SAA7108AE PHILIPS [NXP Semiconductors], SAA7108AE Datasheet - Page 77

• Manufacturer Part Number: SAA7108AE
• Description: HD-CODEC
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
9.6
The SAA7108AE; SAA7109AE incorporates the
generation of a field-locked audio clock, as an auxiliary
function for video capture. An audio sample clock, that is
locked to the field frequency, ensures that there is always
the same predefined number of audio samples associated
with a field, or a set of fields. This ensures synchronous
playback of audio and video after digital recording (e.g.
capture to hard disk), MPEG or other compression or
non-linear editing.
9.6.1
The audio clock is synthesized from the same crystal
frequency as the line-locked video clock is generated. The
master audio clock is defined by the parameters:
Table 35 Programming examples for audio master clock generation
2004 Jun 29
AMCLK = 256
AMCLK = 256
AMCLK = 256
FREQUENCY
HD-CODEC
CRYSTAL
24.576
24.576
24.576
(MHz)
32.11
32.11
32.11
Audio clock generation
(subaddresses 30H to 3FH)
M
ASTER AUDIO CLOCK
48 kHz (12.288 MHz)
44.1 kHz (11.2896 MHz)
32 kHz (8.192 MHz)
FIELD
59.94
59.94
59.94
59.94
59.94
59.94
(Hz)
50
50
50
50
50
50
DECIMAL
245760
205005
225792
188348
225792
188348
163840
136670
163840
136670
ACPF
77
See Table 35 for examples.
Remark: For standard applications the synthesized audio
clock AMCLK can be used directly as master clock and as
input clock for port AMXCLK (short cut) to generate
ASCLK and ALRCLK. For high-end applications it is
recommended to use an external analog PLL circuit to
enhance the performance of the generated audio clock.
Audio master Clocks Per Field, ACPF[17:0] 32H[1:0]
31H[7:0] 30H[7:0] according to the equation:
Audio master Clocks Nominal Increment, ACNI[21:0]
36H[5:0] 35H[7:0] 34H[7:0] according to the equation:
2DFBC
2DFBC
ACPF[17:0]
ACNI[21:0]
320CD
215DE
215DE
3C000
37200
37200
28000
28000
HEX
=
=
SAA7108AE; SAA7109AE
round
round
DECIMAL
3853 517
3210190
3210190
2949362
2949362
3853517
2140127
2140127
2796203
2796203
-------------------------------------------- -
crystal frequency
audio frequency
audio frequency
----------------------------------------- -
field frequency
ACNI
Product specification
3ACCCD
3ACCCD
2AAAAB
2AAAAB
30FBCE
30FBCE
20A7DF
20A7DF
2D00F2
2D00F2
2
23
HEX